The Collaborative International Dictionary of English v.0.48:

Singsong \Sing"song`\, n.
   1. Bad singing or poetry.
      [1913 Webster]

   2. A drawling or monotonous tone, as of a badly executed
      song.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Singsong \Sing"song`\, a.
   Drawling; monotonous; having a monotonous cadence.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Singsong \Sing"song`\, v. i.
   To write poor poetry. [R.] --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

singsong
    adj 1: uttered in a monotonous cadence or rhythm as in chanting;
           "their chantlike intoned prayers"; "a singsong manner of
           speaking" [syn: chantlike, intoned, singsong]
    n 1: a regular and monotonous rising and falling intonation
    2: informal group singing of popular songs [syn: singalong,
       singsong]
    v 1: speak, chant, or declaim in a singsong
    2: move as if accompanied by a singsong; "The porters singsonged
       the travellers' luggage up the mountain"

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "singsong":
   alliterating, alliteration, alliterative, assonance, assonant,
   belabored, blah, broken-record, chanting, chime, chiming,
   cliche-ridden, clockwork regularity, constancy, daily round,
   dingdong, drearisome, dreary, drone, dry, dryasdust, dull, dusty,
   even pace, even tenor, everlasting, harping, humdrum,
   invariability, invariable, jingle, jingle-jangle, jog-trot,
   labored, long-winded, monologue, monotone, monotonous,
   monotonousness, monotony, near rhyme, orderliness, pitter-patter,
   prolix, regularity, repeated sounds, repetitiousness,
   repetitiveness, rhyme, rhymed, rhyming, sameliness, sameness,
   slant rhyme, smoothness, stale repetition, tedious, tedium,
   treadmill, trot, undeviation, undifferentiation, uneventful,
   unnecessary repetition, unvariation, unvarying