The Collaborative International Dictionary of English v.0.48:

Leonine \Le"o*nine\ (l[=e]"[-o]*n[imac]n), a. [L. leoninus, fr.
   leo, leonis, lion: cf. F. l['e]onin. See Lion.]
   Pertaining to, or characteristic of, the lion; as, a leonine
   look; leonine rapacity. -- Le"o*nine*ly, adv.
   [1913 Webster]

   Leonine verse, a kind of verse, in which the end of the
      line rhymes with the middle; -- so named from Leo, or
      Leoninus, a Benedictine and canon of Paris in the twelfth
      century, who wrote largely in this measure, though he was
      not the inventor. The following line is an example:
      [1913 Webster]

            Gloria factorum temere conceditur horum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

leonine
    adj 1: of or characteristic of or resembling a lion

The Devil's Dictionary (1881-1906):

LEONINE, adj.  Unlike a menagerie lion.  Leonine verses are those in
which a word in the middle of a line rhymes with a word at the end, as
in this famous passage from Bella Peeler Silcox:

    The electric light invades the dunnest deep of Hades.
    Cries Pluto, 'twixt his snores:  "O tempora! O mores!"

    It should be explained that Mrs. Silcox does not undertake to
teach pronunciation of the Greek and Latin tongues.  Leonine verses
are so called in honor of a poet named Leo, whom prosodists appear to
find a pleasure in believing to have been the first to discover that a
rhyming couplet could be run into a single line.