From WordNet (r) 2.0 (August 2003) [wn]:
begonia
n : any of numerous plants of the genus Begonia grown for their
attractive glossy asymmetrical leaves and colorful
flowers in usually terminal cymes or racemes
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Begonia \Be*go"ni*a\ (b[-e]*g[=o]"n[i^]*[.a]), n. [From Michel
Begon, a promoter of botany.] (Bot.)
A genus of plants, mostly of tropical America, many species
of which are grown as ornamental plants. The leaves are
curiously one-sided, and often exhibit brilliant colors.
[1913 Webster]