Breadcrumb Home > Dictionary > Index D diam.: Meaning and Definition of Find definitions for: diam. Pronunciation: [key] diameter. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: diam (Thesaurus) dialyzer diamagnet ✖ Related Content Daily Word Quiz: tendentious Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language