Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
thunderclap is a noun meaning "a single sharp crash of thunder". It carries 2 recorded senses.
a single sharp crash of thunder
a shocking surprise
“news of the attack came like a bombshell”
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 thunderclap come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.