Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
warm-up is a noun meaning "exercising in preparation for strenuous activity". It carries one recorded sense.
exercising in preparation for strenuous activity
Definitions, synonyms and semantic relations for warm-up come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.