The Collaborative International Dictionary of English v.0.48:

Lecher \Lech"er\, n. [OE. lechur, lechour, OF. lecheor, lecheur,
   gormand, glutton, libertine, parasite, fr. lechier to lick,
   F. l['e]cher; of Teutonic origin. See Lick.]
   A man given to lewdness; one addicted, in an excessive
   degree, to the indulgence of sexual desire, or to illicit
   sexual relations with women; also called letch and lech.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lecher \Lech"er\, v. i. [imp. & p. p. Lechered; p. pr. & vb.
   n. Lechering.]
   To practice lewdness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lecher
    n 1: man with strong sexual desires [syn: satyr, lecher,
         lech, letch]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "lecher":
   Priapus, aphrodisiomaniac, backslider, bad egg, bad lot,
   black sheep, degenerate, dirty old man, eroticomaniac, erotomaniac,
   fallen angel, goat, gynecomaniac, heartbreaker, lady-killer,
   libertine, lost sheep, lost soul, masher, miscreant, old goat,
   pervert, philander, philanderer, pimp, profligate, recidivist,
   recreant, reprobate, satyr, scapegrace, seducer, skirt chaser,
   sorry lot, trollop, whore, whoremaster, whoremonger, wolf,
   woman chaser