The Collaborative International Dictionary of English v.0.48:

Adonic \A*don"ic\, a. [F. adonique: cf. L. Adonius.]
   Relating to Adonis, famed for his beauty. -- n. An Adonic
   verse.
   [1913 Webster]

   Adonic verse, a verse consisting of a dactyl and spondee
      (-- [crescent] [crescent] | -- --).
      [1913 Webster]