|a macaque monkey, Macaca mulatta, of S Asia: used extensively in medical research|
|[C19: New Latin, arbitrarily from Greek Rhesos|
|rhesus monkey (rē'səs) Pronunciation Key
A small, yellowish-brown monkey (Macaca mulatta) of India, widely used in biological and medical research. The Rh (Rhesus) factor was first discovered in rhesus monkeys.