The Collaborative International Dictionary of English v.0.48:

Alcaic \Al*ca"ic\, a. [L. Alca["i]cus, Gr. ?.]
   Pertaining to Alc[ae]us, a lyric poet of Mitylene, about 6000
   b. c. -- n. A kind of verse, so called from Alc[ae]us. One
   variety consists of five feet, a spondee or iambic, an
   iambic, a long syllable, and two dactyls.
   [1913 Webster] Alcaid

WordNet (r) 3.0 (2006):

Alcaic
    n 1: verse in the meter used in Greek and Latin poetry
         consisting of strophes of 4 tetrametric lines; reputedly
         invented by Alcaeus [syn: Alcaic, Alcaic verse]