/ Dictionary / Index U undersize: Meaning and Definition of Find definitions for: un•der•size Pronunciation: (un'dur-sīz'), [key] — adj. undersized. (of screened minerals) passing through a sieve of given mesh. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: undersize (Thesaurus) undersigned undersized Related Content Daily Word Quiz: inutiae Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language