/ Thesaurus / I Synonyms of index case Find synonyms for: Noun1. index case, patientusage: the earliest documented case of a disease that is included in an epidemiological studyWordNet 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