/ Dictionary / Index H histamine blocker: Meaning and Definition of Find definitions for: his'tamine block"er Pronunciation: [key] — Pharm. Pharm. any of various substances that act at a specific receptor site to block certain actions of histamine. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. histamine histamine headache Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language