Definition of: ageratum

(aj′ə·rā′təm, ə·jer′ə·təm) noun
1. Any of a large genus (Ageratum) of tropical American herbs of the family Compositae or Asteraceae with opposite petioled leaves and terminal cymes or panicles of blue or white flowers in small heads.
2. Any of several plants having similar heads of blue flowers. [<NL <Gk. agē raton, a kind of plant < agēratos ageless < a- not + gēras old age]