noun
1.
a. : a plant of the genus Oxalis ; especially : a white-flowered to reddish flowered stemless herb ( O. montana ) with trifoliate leaves that is sometimes considered to be the original shamrock
b. : any of several yellow-flowered plants of the related genus Xanthoxalis
2. : sheep sorrel 1
3. : a West Indian begonia ( Begonia acutifolia )