Webster's New World Medical Dictionary

adult-onset Still’s disease
Still’s disease that
begins in adulthood rather than in childhood. See
also 
Still’s disease.
advance directive
A document drawn up by a
patient or, in some cases, the patient’s representa-
tive to set treatment preferences and to designate a
surrogate decision maker should the patient
become unable to make medical decisions. Advance
directives include the living will, power of attorney,
and health care proxy. See also 
DNR.
adverse event
In pharmacology, any unexpected
or dangerous reaction to a drug or vaccine.
AED
See 
automated external defibrillator.
aer-, aero
- Prefix indicating air or gas, such as
aerogastria (excess stomach gas).
aerobic
Oxygen-requiring. Aerobic bacteria need
oxygen to grow. Aerobic exercise requires the heart
and lungs to work harder to meet the body’s
increased oxygen demand.
aerobic exercise
Brisk exercise that promotes
the circulation of oxygen through the blood and is
associated with an increased rate of breathing.
Examples include running, swimming, and bicy-
cling.
aerophagia
Literally, eating air, from the Greek
words 
aer,
meaning “air,” and 
phagein,
meaning
“to eat.” Aerophagia is a common cause of stomach
gas. Everyone swallows small amounts of air when
eating or drinking. However, activities such as rapid
eating or drinking, gum chewing, smoking, and
wearing ill-fitting dentures may cause a significant
increase in swallowed air.
aerosinusitis
Painful sinus troubles due to
changing atmospheric pressures. Aerosinusitis is
the cause of sinus pain when going up or down in a
plane. Also known as barosinusitis and sinus baro-
trauma.