any tropical American plant of the genus Ageratum, such as A. houstonianum and A. conyzoides, which have thick clusters of purplish-blue flowers
Word origin
C16: New Latin, via Latin from Greek agēraton that which does not age, from a-1 + gērat-, stem of gēras old age; the flowers of the plant remain vivid for a long time
ageratum in American English
(ˌædʒərˈeɪtəm)
noun
any of several plants (genus Ageratum) of the composite family with small, thick heads of usually bluish flowers: widely used as border plants in gardens
Word origin
ModL < Gr agēraton, a kind of plant < agēratos, not growing old < a-, not + gēras, old age