From WordNet (r) 2.0 (August 2003) [wn]:
asymmetry
n : (mathematics) a lack of symmetry [syn: imbalance] [ant:
symmetry]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Asymmetry \A*sym"me*try\, n. [Gr. ?; 'a priv. + ? symmetry.]
1. Want of symmetry, or proportion between the parts of a
thing, esp. lack of bilateral symmetry.
[1913 Webster]
2. (Math.) Incommensurability. [Obs.] --Barrow.
[1913 Webster]