The Collaborative International Dictionary of English v.0.48:

Mentha \Men"tha\, n. [L. See Mint the plant.] (Bot.)
   A widely distributed genus of fragrant herbs, including the
   peppermint, spearmint, etc. The plants have small flowers,
   usually arranged in dense axillary clusters.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Mentha
    n 1: mint plants [syn: Mentha, genus Mentha]