/ Dictionary / Index A armillaria root rot: Meaning and Definition of Find definitions for: ar•mil•lar'i•a root' rot" Pronunciation: (är"mu-lâr'ē-u), [key] a widespread rot caused by the honey mushroom, Armillariella mellea, seriously damaging to the roots of various hardwoods, conifers, and other trees. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. armilla armillary Related Content Daily Word Quiz: agitated Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language