smirk
n. countablen. a smile that shows you are very pleased with yourself or that you find something funny in a mean way. It often looks like you are hiding a secret or making fun of someone.
n. a smug, conceited, or silly smile. Often implies a sense of superiority, derision, or suppressed amusement.
He had a self-satisfied smirk on his face.
She couldn't hide her smirk when she realized she had won the argument.
The witness's persistent smirk during the cross-examination suggested a lack of respect for the proceedings, eventually prompting a stern warning from the judge.
From Middle English smirken, from Old English smearcian (“to smile”), corresponding to smerian + -cian (English -k; compare talk and stalk from, respectively, tell and steal). The former element from Proto-Germanic smarōną (“to mock, scoff at”), and the latter from Proto-Germanic -kōną. Compare Middle High German smielen/smieren (“to smile”) ( > obsolete, rare German schmieren). Doublet of smile. The specific meaning of a mocking or unpleasant, malicious smile or grin develops in Early Modern English, but until the 18th century, it could still be used to describe a generic smile.