/ Dictionary / Index E efficacity: Meaning and Definition of Find definitions for: ef•fi•cac•i•ty Pronunciation: (ef"i-kas'i-tē), [key] — pl. -ties. efficacy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. efficacious efficacy Related Content Daily Word Quiz: ingenuity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language