A sneer is defined by the raising or curling of this
to show contempt, as by
... [DOC] [TLE] sneer - definition and meaning - Wordnik [PAR] sneer: A scornful facial expression characterized by a slight raising of one corner 
... of contempt or scorn; the upper lip curls; v. express through a scornful smile... [DOC] [TLE] Curl of the lip - definition, etymology and usage, examples and ... [PAR] Definition of Curl of the lip in the Fine Dictionary.