The Collaborative International Dictionary of English v.0.48:

Anthodium \An*tho"di*um\, n. [NL., from Gr. ? like flowers,
   flowery; 'a`nqos flower + e'i^dos form.] (Bot.)
   The inflorescence of a compound flower in which many florets
   are gathered into a involucrate head.
   [1913 Webster]