/ smɜːk; NAmE smɜːrk/ verb
[ v ] to smile in a silly or unpleasant way that shows that you are pleased with yourself, know sth that other people do not know, etc. :
It was hard not to smirk.
He smirked unpleasantly when we told him the bad news.
► smirk noun :
She had a self-satisfied smirk on her face.
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WORD ORIGIN
Old English sme(a)rcian , from a base shared by smile . The early sense was to smile ; it later gained a notion of smugness or silliness.