Source : Webster's Revised Unabridged Dictionary (1913)

Legato \Le*ga"to\ (l[asl]*g[aum]"t[-o]), a. [It., tied, joined,
   fr. legare to tie, bind, L. ligare.] (Mus.)
   Connected; tied; -- a term used when successive tones are to
   be produced in a closely connected, smoothly gliding manner.
   It is often indicated by a tie, thus ?, ?, or ?, ?, written
   over or under the notes to be so performed; -- opposed to
   {staccato}.

Source : WordNet®

legato
     adj : without breaks between notes; smooth and connected; "a
           legato passage" [syn: {smooth}] [ant: {staccato}]
     adv : connecting the notes; in music; "play this legato, please"
           [ant: {staccato}]