Grimace /(grĭm"ĭs [or] grĭ*mās")/

Gri·mace

Grimace

n.
  1. A distortion of the countenance, whether habitual, from affectation, or momentary and occasional, to express some feeling, as contempt, disapprobation, complacency, etc.; a smirk; a made-up face.
    Moving his face into such a hideous grimace, that every feature of it appeared under a different distortion.

Grimace

v. i.
  1. To make grimaces; to distort one's face; to make faces.