A small hillock or mound, particularly in dialectal or regional British English.
Possibly from 'bump' plus '-ock' diminutive suffix (as in 'hillock', 'hammock'), or from Old English/Germanic roots for a small elevated feature.
British English regional words for terrain features are incredibly specific—'bummock,' 'knoll,' 'tor,' 'fell'—because people who spent their lives in landscapes needed precise vocabulary.
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