/ Dictionary / Index F Forbush decrease: Meaning and Definition of Find definitions for: For'bush de"crease Pronunciation: (fôr'boosh), [key] — Astron. Astron. the sudden decrease in the intensity of cosmic rays after an increase in solar activity. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. forborne forby Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language