From The Collaborative International Dictionary of English v.0.48 :
bimodal \bimodal\ adj. (Statistics)
having or occurring with two modes[9]; having two maxima;
-- of a curve or distribution. unimodal
[WordNet 1.5]
From WordNet (r) 3.0 (2006) :
bimodal
adj 1: of a distribution; having or occurring with two modes
[ant: unimodal]