/ Dictionary / Index W working fluid: Meaning and Definition of Find definitions for: work'ing flu'id Pronunciation: [key] — Mech. Mech. a liquid or gaseous working substance. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. working face working girl Related Content Daily Word Quiz: benevolent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language