The Collaborative International Dictionary of English v.0.48:

Asymmetric \As`ym*met"ric\, Asymmetrical \As`ym*met"ri*cal\, a.
   [See Asymmetrous.]
   1. Incommensurable. [Obs.]
      [1913 Webster]

   2. Not symmetrical; wanting proportion; esp., not bilaterally
      symmetrical. --Huxley.
      [1913 Webster]

WordNet (r) 3.0 (2006):

asymmetrical
    adj 1: characterized by asymmetry in the spatial arrangement or
           placement of parts or components [syn: asymmetrical,
           asymmetric] [ant: symmetric, symmetrical]
    2: irregular in shape or outline; "asymmetrical features"; "a
       dress with a crooked hemline" [syn: asymmetrical,
       crooked]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "asymmetrical":
   anamorphous, askew, asymmetric, bent, bowed, cockeyed, contorted,
   crazy, crooked, crumpled, crunched, deviative, disparate,
   disproportionate, distorted, ill-matched, ill-sorted, inadequate,
   insufficient, irregular, labyrinthine, lopsided, mismatched,
   nonsymmetric, odd, one-sided, out of proportion, skew, skewed,
   sprung, tortuous, twisted, unequal, uneven, unsymmetric, warped