- noun:
- any one of a number of flowers for the genera Spermacoce and Diodia, of the madder household.
- title of a few flowers of genera Spermacoce and Diodia, associated with Madder household.
- A name fond of a number of rubiaceous flowers of the genera Spermacoce, Diodia, and Borreria.
- The knapweed, Centaurea nigra.
How would you define buttonweed?