/ Dictionary / Index A allergen: Meaning and Definition of Find definitions for: al•ler•gen Pronunciation: (al'ur-jun, -jen"), [key] — n. Immunol. any substance, often a protein, that induces an allergy: common allergens include pollen, grasses, dust, and some medications. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: allergen (Thesaurus) Alleppey allergenic Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language