/aj'euh ray"teuhm, euh jer"euh-/ , n.
1. any of several composite plants of the genus Ageratum, esp. A. houstonianum, having heart-shaped leaves and small, dense, blue, lavender, or white flower heads, often grown in gardens.
2. any of various other composite plants, as the mistflower, having blue or white flowers.
[ 1560-70; ageraton agératon, neut. of agératos unaging, equiv. to a- A- 6 + gerat- (s. of gêras ) old age + -os adj. suffix ]