IPA: /ˈsmɪrkər/
KK: /ˈsmɪrkər/
A person who smiles in a way that shows they are pleased with themselves, often in a way that annoys others.
He was such a smirker that everyone found his smile irritating.
Smirker → The word is formed from 'smirk' (from Middle English *smerke*, meaning to smile in a smug or self-satisfied way) and '-er' (meaning a person who). A smirker is a person who smiles in a smug or self-satisfied manner.
Think of someone who smiles in a smug way — that's what a smirker does, as the root 'smirk' refers to that kind of smile.