/ Dictionary / Index H holmium: Meaning and Definition of Find definitions for: hol•mi•um Pronunciation: (hōl'mē-um), [key] — n. Chem. a rare-earth, trivalent element found in gadolinite. Symbol: Ho; at. wt.: 164.930; at. no.: 67. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: holmium (Thesaurus) holmic holm oak Related Content Daily Word Quiz: placate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language