The Collaborative International Dictionary of English v.0.48:

Paean \P[ae]"an\ (p[=e]`an), n. [L. paean, Gr. paia`n, fr.
   Paia`n the physician of the gods, later, Apollo. Cf.
   P[ae]on, Peony.] [Written also pean.]
   1. An ancient Greek hymn in honor of Apollo as a healing
      deity, and, later, a song addressed to other deities.
      [1913 Webster]

   2. Any loud and joyous song; a song of triumph, joy, or
      praise. --Dryden. "Public p[ae]ans of congratulation."
      --De Quincey.
      [1913 Webster]

   3. See P[ae]on.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

paeon \p[ae]"on\ (p[=e]"[o^]n), n. [L. paeon, Gr. paiw`n a
   solemn song, also, a p[ae]on, equiv. to paia`n. See
   P[ae]an.] (Anc. Poet.)
   A foot of four syllables, one long and three short, admitting
   of four combinations, according to the place of the long
   syllable. [Written also, less correctly, p[ae]an.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

paean
    n 1: a formal expression of praise [syn: encomium, eulogy,
         panegyric, paean, pean]
    2: (ancient Greece) a hymn of praise (especially one sung in
       ancient Greece to invoke or thank a deity) [syn: paean,
       pean]