poinsettia(n = noun.plant) christmas flower, christmas star, euphorbia pulcherrima, lobster plant, mexican flameleaf, painted leaf - tropical American plant having poisonous milk and showy tapering usually scarlet petallike leaves surrounding small yellow flowers;
is a kind of spurge
is a member of euphorbia, genus euphorbia

   A Mexican shrub (Euphorbia pulcherrima) with very large and conspicuous vermilion bracts below the yellowish flowers. [1913 Webster]

poinsettia, n. a shrub, Euphorbia pulcherrima, with large showy scarlet or pink bracts surrounding small yellow flowers.

Etymology:
mod.L f. J. R. Poinsett, Amer. diplomat d. 1851

japanese poinsettia, poinsettia strain