Webster's New World Medical Dictionary

OPV
Oral polio vaccine. See 
polio vaccine, oral.
OR
Operating room.
oral
Having to do with the mouth. For example,
an oral solution is a solution that is given by mouth.
oral cancer
Cancer within the mouth. Oral can-
cer is associated with smoking cigarettes and cigars
as well as chewing tobacco. It is generally noticed as
a painless growth on the inner cheek, gum, or
tongue. Treatment options include surgical resec-
tion, radiation, and/or chemotherapy.
oral contraceptive
A birth control pill taken by
mouth. Most oral contraceptives include both estro-
gen and progestogen. When given in certain
amounts and at certain times in the menstrual cycle,
these hormones prevent the ovary from releasing an
egg for fertilization. Colloquially known as “the
pill.” See also 
birth control; contraceptive.
oral polio vaccine
See 
polio vaccine, oral.
oral rehydration solution
A specially designed
liquid that contains water, glucose, and electrolytes
and is given to treat dehydration. Abbreviated ORS.
oral rehydration therapy
The administration
of special fluids by mouth to treat dehydration.
Abbreviated ORT. See also 
oral rehydration
solution.
oral surgeon
A dentist who has special training
in surgery to correct problems of the mouth and jaw.
oral
-
motor
Relating to the muscles of the mouth
and/or to movements of the mouth.
oral
-
motor apraxia of speech
See 
apraxia of
speech.
orbit
In medicine, the bony cavity in which the
eyeball sits.
orbital
In anatomy, pertaining to the orbit, the
bony cavity that contains the eyeball.