/ Thesaurus / R Synonyms of rtlt Find synonyms for: Noun1. round-trip light time, RTLT, elapsed timeusage: the elapsed time it takes for a signal to travel from Earth to a spacecraft (or other body) and back to the starting pointWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: abominable Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language