A person or thing that dunts; something that strikes or bumps (Scottish dialect).
From 'dunt' plus the agent suffix '-er', creating an occupational or descriptive noun. This follows the productive pattern of -er agent nouns in English (like 'runner' or 'hammer').
Scottish English is wonderfully practical in its word-making—'dunter' just means whatever does the dunting, which could be a person, a machine, or just a thing that bumps into you, showing how -er nouns capture causation in action.
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