/ Thesaurus / I Synonyms of index number Find synonyms for: Noun1. index, index number, indicant, indicator, factusage: a number or ratio (a value on a scale of measurement) derived from a series of observed facts; can reveal relative changes as a function of timeWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: penury Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language