/ Dictionary / Index J jamproof: Meaning and Definition of Find definitions for: jam•proof Pronunciation: ( jam'prf"), [key] — adj. built so as to prevent jamming: a jamproof copying machine. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. jam-pack jams Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language