Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
countersink is a noun and verb meaning "a hole (usually in wood) with the top part enlarged so that a screw or bolt will fit into it and lie below the surface". It carries 3 recorded senses.
a hole (usually in wood) with the top part enlarged so that a screw or bolt will fit into it and lie below the surface
a bit for enlarging the upper part of a hole
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for countersink come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.