Any of various arboreal rodents of the genus Sciurus and related genera of the family Sciuridae, having a long flexible bushy tail and including the fox squirrel, gray squirrel, and red squirrel. Also called tree squirrel. Any of various other rodents of the family Sciuridae, as the ground squirrel or the flying squirrel. The fur of one of these rodents. To hide or store: squirreled away her money.