The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

legato
    adv 1: connecting the notes; in music; "play this legato,
           please" [ant: staccato]
    adj 1: (music) without breaks between notes; smooth and
           connected; "a legato passage" [syn: legato, smooth]
           [ant: disconnected, staccato]

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "legato":
   a cappella, abbandono, accrescendo, adagietto, adagio, affettuoso,
   agilmente, agitato, allegretto, allegro, amabile, amoroso, andante,
   andantino, appassionatamente, appassionato, brillante, cantando,
   capriccioso, con affetto, con agilita, con agitazione, con amore,
   crescendo, decrescendo, demilegato, diminuendo, dolce, execution,
   expression, fingering, forte, fortissimo, glissando, intonation,
   lamentabile, larghetto, larghissimo, largo, leggiero, marcando,
   mezzo staccato, morendo, music-making, parlando, performance,
   pianism, pianissimo, piano, pizzicato, prestissimo, presto,
   rallentando, rendering, rendition, repercussion, ritardando,
   ritenuto, rubato, scherzando, scherzo, scherzoso, slur, sordo,
   sotto voce, spiccato, staccato, stretto, touch, tremolando,
   tremoloso, trillando