/ Dictionary / Index V visna: Meaning and Definition of Find definitions for: vis•na Pronunciation: (vis'nu), [key] — n. a disease of sheep, caused by a quickly mutating lentivirus, and affecting the central nervous system. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. vis major visor Related Content Daily Word Quiz: feral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language