/ Dictionary / Index U undersign: Meaning and Definition of Find definitions for: un•der•sign Pronunciation: (un"dur-sīn', un'dur-sīn"), [key] — v.t. to sign one's name under or at the end of (a letter or document); affix one's signature to. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: undersign (Thesaurus) underside undersigned Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language