Webster's New World Medical Dictionary

acromegaly
See 
gigantism, pituitary.
acromioclavicular joint
A gliding joint located
between the acromion (a projection of the scapula
that forms the point of the shoulder) and the clavi-
cle (the collar bone). It is served and supported by
the capsular, superior, and inferior acromioclavicu-
lar ligaments; the articular disk; and the coraco-
clavicular (trapezoid and conoid) ligaments.
Abbreviated AC joint.
acrosyndactyly
A condition in which a person
has fused or webbed fingers or toes. Acrosyndactyly
can be partial or complete, and it can usually be
corrected via surgery. It is associated with several
birth defect syndromes. See also 
Apert syndrome.
ACS
American College of Surgeons, a professional
organization that administers standards of practice
for surgeons. Those who meet the group’s standards
can call themselves Fellows of the ACS.
actinic
Referring to the ultraviolet (UV) rays from
sunlight and UV lamps. Sunburn is an actinic burn.
An actinic keratosis is a skin lesion that is the con-
sequence of chronic sun exposure.
actinic keratosis
Rough, scaly patches of skin
that are considered precancerous and are due to
sun exposure. Prevention is to cut sun exposure and
wear sunscreen. Treatments include performing
cryosurgery (freezing with liquid nitrogen), cutting
the keratoses away, burning them, putting 5-fluo-
rouracil on them, and using photodynamic therapy
(injecting into the bloodstream a chemical that col-
lects in actinic keratoses and makes them more sen-
sitive to destruction by a specialized form of light).
Also known as solar keratosis and senile keratosis.
activated charcoal
Charcoal that has been
heated to increase its ability to absorb molecules.
Activated charcoal is used to help relieve intestinal
gas. It is also used to filter and purify liquids, to
absorb poisons (as in gas mask filters), and in emer-
gency situations to neutralize swallowed poisons.