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):

asymmetric
    adj 1: characterized by asymmetry in the spatial arrangement or
           placement of parts or components [syn: asymmetrical,
           asymmetric] [ant: symmetric, symmetrical]