/ Dictionary / Index B black rust: Meaning and Definition of Find definitions for: black' rust' Pronunciation: [key] — Plant Pathol. Plant Pathol. any of several diseases of plants caused by rusts and characterized by black discoloration resulting from the fungal teliospores. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Black Russian black sage Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language