A person who gripes frequently; someone who complains persistently or annoyingly.
From 'gripe' (to complain) plus the agent noun suffix '-er' (one who does the action), created following the productive English pattern of turning verbs into 'one who does X' nouns.
Every verb can potentially become an agent noun with '-er'—'run' → 'runner,' 'teach' → 'teacher,' 'gripe' → 'griper.' This flexibility is why English speakers can coin new job titles and character descriptions instantly!
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