A person who glowers; someone who stares angrily or disapprovingly.
From 'glower' + '-er' (agent noun suffix). Someone who performs the action of glowering.
The '-er' suffix is incredibly productive in English—almost any verb can become 'a _____er' (a person who does that thing)—so even unusual words like 'glower' instantly become 'glowerer' and everyone understands it!
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