/ Dictionary / Index M metalloid: Meaning and Definition of Find definitions for: met•al•loid Pronunciation: (met'l-oid"), [key] — n. a nonmetal that in combination with a metal forms an alloy. an element that has both metallic and nonmetallic properties, as arsenic, silicon, or boron. —adj. of or pertaining to a metalloid. resembling both a metal and a nonmetal. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: metalloid (Thesaurus) metallography metallo-organic Related Content Daily Word Quiz: fervor Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language