The Collaborative International Dictionary of English v.0.48:

Lyre \Lyre\, n. [OE. lire, OF. lyre, L. lyra, Gr. ?. Cf.
   Lyra.]
   1. (Mus.) A stringed instrument of music; a kind of harp much
      used by the ancients, as an accompaniment to poetry.
      [1913 Webster]

   Note: The lyre was the peculiar instrument of Apollo, the
         tutelary god of music and poetry. It gave name to the
         species of verse called lyric, to which it originally
         furnished an accompaniment.
         [1913 Webster]

   2. (Astron.) One of the constellations; Lyra. See Lyra.
      [1913 Webster]

   Lyre bat (Zool.), a small bat (Megaderma lyra),
      inhabiting India and Ceylon. It is remarkable for the
      enormous size and curious shape of the nose membrane and
      ears.

   Lyre turtle (Zool.), the leatherback.
      [1913 Webster]

WordNet (r) 3.0 (2006):

lyre
    n 1: a harp used by ancient Greeks for accompaniment

The Devil's Dictionary (1881-1906):

LYRE, n.  An ancient instrument of torture.  The word is now used in a
figurative sense to denote the poetic faculty, as in the following
fiery lines of our great poet, Ella Wheeler Wilcox:

    I sit astride Parnassus with my lyre,
    And pick with care the disobedient wire.
    That stupid shepherd lolling on his crook
    With deaf attention scarcely deigns to look.
    I bide my time, and it shall come at length,
    When, with a Titan's energy and strength,
    I'll grab a fistful of the strings, and O,
    The word shall suffer when I let them go!
                                                    Farquharson Harris