squir·rel (skwûr′əl, skwŭr′-) n. 1. Any of various arboreal rodents of the tribe Sciurini and especially of the genus Sciurus, characteristically having a long flexible bushy tail. Also called tree squirrel. 2. Any of various other rodents of the family Sciuridae, such as the ground squirrels and the flying squirrels. 3. The fur of one of these …