Dictionary

Enter a word or phrase below to search our online dictionary of over 1,300 general medical terms, or click on a letter of the alphabet to view all terms beginning with that letter:

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Search for 'M'

Phrase	Definition
macrophage	A large cell that engulfs and digests foreign material.
macula	The central part of the retina with the highest density of light receptors. Responsible for detailed vision.
macule	A discolored, flat spot of skin.
malady	Illness.
malaria	An infectious disease of the tropics characterized by high fever and chills. The fever typically recurs every third day. Some forms of malaria can be fatal.
malignancy	A tendency to worsen to a more serious illness or death. Commonly used to describe cancer.
malingering	Deliberate exaggeration of the symptoms of an illness or injury for gain. For example, pretending to be ill in order to escape duty or work.
malleolus	The rounded bony prominence on either side of the ankle.
malleus	A small bone in the middle ear, often called the hammer.
malnutrition	Poor nourishment resulting from an inadequate or improper diet.
malocclusion	Improper meeting of the upper and lower teeth.
malunion	Improper healing of the pieces of a broken bone.
mammary	Having to do with the breast.
mandible	The lower jaw.
mania	A mental disorder. Characterized by extreme excitement and energy.
manic-depressive	A mental disorder marked by alternating periods of excitability and depression. Also called bipolar affective disorder.
marijuana	A drug derived from the leaves of the Cannabis sativa plant. Makes the user feel euphoric.
marrow	The soft, sponge-like material inside the bones.
masculinization	Development of male sex characteristics in a female.
masochism	Pleasure from personal, psychological or physical pain.
mastectomy	Surgical removal of the breast.
mastitis	Inflammation of the breast.
mastoid	A bony, rounded projection of the skull located behind each ear.
mastoiditis	An infection of the mastoid bone that can cause redness, warmth, swelling and pain behind the ear, sometimes with drainage from the ear.
masturbation	Sexual self-stimulation.
maxillae	The pair of bones forming the upper jaw.
measles	A highly contagious viral disease occurring most frequently in childhood and characterized by small, red spots on the skin, high fever and nasal discharge.
Meckel's diverticulum	A sac that may form in the small intestine, present at birth.
meconium	The greenish fecal matter in a fetus, forming the first bowel movement of a newborn infant.
median nerve	The nerve that stimulates some of the muscles of the hand and wrist.
mediastinum	The tissues and organs located directly behind the sternum between the lungs. Contains the heart and its large vessels, the esophagus, thymus, lymph nodes and other structures and tissues.
medulla	The inner part of an organ. The adrenal medulla is the center of the adrenal gland where epinephrine (adrenaline) is produced.
medulla oblongata	The part of the brain just above the spinal cord that includes the control centers for breathing, circulation and heartbeat.
meibomian gland	A type of gland of the eyelid's inner surface. Inflammation of a meibomian gland can produce a swelling called a chalazion.
melancholia	A mental state characterized by extreme sadness. A severe form of depression.
melanin	A brownish-black pigment normally found in skin, hair and parts of the eye.
melanoma	A dark-colored tumor, especially malignant melanoma, that is a form of skin cancer that can spread from one part of the body to another.
melasma	Dark coloring of the skin often seen during pregnancy and at menopause. Also occurs in Addison's disease.
melena	Black-colored feces caused by the presence of blood.
membrane	A thin layer of tissue covering an organ.
menarche	A woman's first menstrual period.
Meniere's syndrome	A disorder of the inner ear characterized by dizziness, ringing in the ears and progressive hearing loss.
meninges	The three membranes covering the brain and spinal cord.
meningioma	Tumor of the meninges, usually benign and slow-growing.
meningitis	Inflammation of the meninges as the result of infection by bacteria or viruses. Symptoms include high fever, headache, stiff neck and vomiting. This is a life-threatening disease that must be treated promptly.
meniscus	The cartilage in the knee joint.
menopause	The time at which the menstrual cycle gradually stops. Sometimes referred to as the "change of life."
menorrhagia	Heavy bleeding during menstruation.
menstruation	The periodic discharge of blood and tissues from the uterus. This usually occurs about every four weeks in a woman who isn't pregnant. Also called "a period."
metabolism	The chemical and physical processes involved in building up, storing and using materials required for life.
metacarpal	Any of the five bones that make up the hand and join the wrist to the fingers.
metaphysis	The wider portion at the end of a long bone where growth occurs in infants and children.
metastasis	The spread of a disease from its primary site in the body to another location in the body. Usually refers to cancer, but can be used to refer to infection.
metatarsal	Any of the five bones of the foot directly jointed to each of the toes.
metra	Uterus.
metritis	Inflammation of the uterus.
metrorrhagia	Uterine bleeding, usually of normal amount occurring at irregular intervals.
microbe	A microorganism, such as bacterium.
microbiology	The study of living microbes, including bacteria, protozoa and molds.
microencephaly	Having an abnormally small brain.
microorganism	A microscopic plant or animal.
midwife	A person who helps women at childbirth, but who isn't a nurse or physician.
migraine	A group of symptoms that includes a severe headache, usually on one side of the head, and often accompanied by visual disturbances, nausea, irritability and other symptoms.
milia	Pinhead-sized whitish skin lesions found on the face or trunk of some newborn infants.
miliaria	"Prickly heat" or "heat rash" as a result of inflammation of the sweat glands and characterized by small, white or red skin eruptions.
miscarriage	Natural loss of a fetus from the womb before it is sufficiently developed to survive. Also called spontaneous abortion.
mitral valve	The valve of the heart between the left atrium and left ventricle that prevents the flow of blood back into the atrium when the heart muscle is contracting.
mittelschmerz	Pelvic pain between periods, corresponding to the release of an ovum (egg) by an ovary.
mole	1. A fleshy, pigmented skin blemish. 2. A mass of uterine tissue formed by a failure of the normal fertilization process during conception.
molluscum contagiosum	A viral infection of the skin characterized by lesions with depressed centers containing a curd-like substance.
mongolism	A condition present at birth characterized by mental deficiency, a broad face and slanting eyes. Also called Down syndrome.
monocyte	A large white blood cell leukocyte.
mononucleosis	An infection with Epstein-Barr virus. Also called "mono."
morbid	1. Pathologic or abnormal. 2. Having to do with, or characterized by, disease.
morning sickness	Nausea and vomiting occurring during pregnancy.
MRI	Magnetic resonance imaging.
mucosa	The membrane covering canals and cavities that open on the outside of the body, such as the gastrointestinal tract and the respiratory tract. Also called mucous membrane.
mumps	A viral disease of childhood characterized by swelling of the parotid (salivary) glands and fever.
murmur	An extra heart sound that may be normal or abnormal.
muscle	Tissue made up of bundles of long, slender cells that contract when stimulated.
mutation	A damaged gene that may produce a disease or deficiency.
mute	An inability or unwillingness to speak.
myalgia	Muscle pain.
myasthenia gravis	A chronic disease characterized by muscular weakness and fatigue.
myelin	The fat-like substance that insulates certain nerve fibers.
myocarditis	Inflammation of the heart muscle.
myoma	A tumor of muscle cells.
myopia	Nearsightedness.
myositis	Inflammation of a muscle.
myringotomy	An incision in the eardrum to relieve pressure or release fluid.