1. a functionless digit on the foot of some animals, as on the inner side of a dog's leg or above the true hoof in cattle, deer, etc.
2. the claw or hoof at the end of such a digit
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'dewclaw'prob. so called because it does not touch the ground, but only the dew on the surface