[1] : The Collaborative International Dictionary of English v.0.48

sonnet \son"net\, n. f., fr. it. sonetto, fr. suono a sound, a
   song, fr. l. sonus a sound. see sound noise.
   1. a short poem, -- usually amatory. obs. --shak.
      1913 webster

            he had a wonderful desire to chant a sonnet or hymn
            unto apollo pythius.                  --holland.
      1913 webster

   2. a poem of fourteen lines, -- two stanzas, called the
      octave, being of four verses each, and two stanzas, called
      the sestet, of three verses each, the rhymes being
      adjusted by a particular rule.
      1913 webster

   note: in the proper sonnet each line has five accents, and
         the octave has but two rhymes, the second, third,
         sixth, and seventh lines being of one rhyme, and the
         first, fourth, fifth, and eighth being of another. in
         the sestet there are sometimes two and sometimes three
         rhymes; but in some way its two stazas rhyme together.
         often the three lines of the first stanza rhyme
         severally with the three lines of the second. in
         shakespeare's sonnets, the first twelve lines are
         rhymed alternately, and the last two rhyme together.
         1913 webster
see also:
sound 

[2] : The Collaborative International Dictionary of English v.0.48

sonnet \son"net\, v. i.
   to compose sonnets. "strains that come almost to sonneting."
   --milton.
   1913 webster

[3] : WordNet (r) 2.0

sonnet
     n : a verse form consisting of 14 lines with a fixed rhyme
         scheme
     v 1: praise in a sonnet
     2: compose a sonnet

[4] : Moby Thesaurus II by Grady Ward, 1.0

67 moby thesaurus words for "sonnet":
   english sonnet, horatian ode, italian sonnet, petrarchan sonnet,
   pindaric ode, sapphic ode, shakespearean sonnet, alba, anacreontic,
   balada, ballad, ballade, bucolic, canso, chanson, clerihew, dirge,
   dithyramb, eclogue, elegy, epic, epigram, epithalamium, epode,
   epopee, epopoeia, epos, georgic, ghazel, haiku, idyll, jingle,
   limerick, lyric, madrigal, monody, narrative poem, nursery rhyme,
   ode, palinode, pastoral, pastoral elegy, pastorela, pastourelle,
   poem, prothalamium, rhyme, rondeau, rondel, roundel, roundelay,
   satire, sestina, sloka, song, sonnet sequence, tanka, tenso,
   tenzone, threnody, triolet, troubadour poem, verse, verselet,
   versicle, villanelle, virelay

Sonnet >> S Words
Sonnet, definition of term: Sonnet
sonnet_pag1.html

Italian Sonnet >> I Words
Italian Sonnet, definition of term: Italian Sonnet
italian+sonnet_pag1.html

English Sonnet >> E Words
English Sonnet, definition of term: English Sonnet
english+sonnet_pag1.html