Clinical Nurse Specialist, RN. After graduating from nursing school in Japan, I worked for two years in a large Tokyo hospital.
The definition of a stool is a seat without arms supported by three or four legs. An example of a stool is a seat that you'd sit on at a bar. Stool is the waste matter in a bowel movement. An example of stool is the source of the sample provided to a medical lab to check for stomach parasites. a piece of furniture for one person to sit on, typically having a round seat, three or four legs or a central post, and no back or arms.
A decoy or informer, especially a police spy. For example, Watch out for Doug; I'm sure he's a stool pigeon for the supervisor. This term alludes to a bird tied to a stool or similar perch in order to attract other birds, which will then be shot. However, one writer believes that stool is a variant for stale or stall, both nouns used for a decoy bird before 1500 or so. [ c. 1820 ]