/ Thesaurus / E Synonyms of extremely low frequency Find synonyms for: Noun1. extremely low frequency, ELF, radio frequencyusage: below 3 kilohertzWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language