Source : Webster's Revised Unabridged Dictionary (1913)

Leer \Leer\, v. t.
   To entice with a leer, or leers; as, to leer a man to ruin.
   --Dryden.

Leer \Leer\ (l[=e]r), v. t.
   To learn. [Obs.] See {Lere}, to learn.

Leer \Leer\, a. [OE. lere; akin to G. leer, OHG. & OS. l[=a]ri.]
   [Obs. or Prov. Eng.]
   Empty; destitute; wanting; as:
   (a) Empty of contents. ``A leer stomach.'' --Gifford.
   (b) Destitute of a rider; and hence, led, not ridden; as, a
       leer horse. --B. Jonson.
   (c) Wanting sense or seriousness; trifling; trivolous; as,
       leer words.

Leer \Leer\, n.
   An oven in which glassware is annealed.

Leer \Leer\, n. [OE. lere cheek, face, look, AS. hle['o]r cheek,
   face; akin to OS. hlear, hlior, OD. lier, Icel. hl[=y]r.]
   1. The cheek. [Obs.] --Holinshed.

   2. Complexion; aspect; appearance. [Obs.]

            A Rosalind of a better leer than you. --Shak.

   3. A distorted expression of the face, or an indirect glance
      of the eye, conveying a sinister or immodest suggestion.

            With jealous leer malign Eyed them askance.
                                                  --Milton.

            She gives the leer of invitation.     --Shak.

            Damn with faint praise, assent with civil leer.
                                                  --Pope.

Leer \Leer\, v. i. [imp. & p. p. {Leered} (l[=e]rd); p. pr. &
   vb. n. {Leering}.]
   To look with a leer; to look askance with a suggestive
   expression, as of hatred, contempt, lust, etc.; to cast a
   sidelong lustful or malign look.

         I will leerupon him as a' comes by.      --Shak.

         The priest, above his book, Leering at his neighbor's
         wife.                                    --Tennyson.

Source : WordNet®

leer
     n 1: a facial expression of contempt or scorn; the upper lip
          curls [syn: {sneer}]
     2: a suggestive or sneering look or grin
     v : look suggestively or obliquely; look or gaze with a sly,
         immodest, or malign expression; "The men leered at the
         young women on the beach"