Webster’s New World College Dictionary noun1. jack (sense 13) jack (sense 13c)2. [pl., with sing. v.] jack noun
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< dial. checkstone, chackstone < check, chuck, pebble