Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
1-hitter is a noun meaning "a game in which a pitcher allows the opposing team only one hit". It carries one recorded sense.
a game in which a pitcher allows the opposing team only one hit
Definitions, synonyms and semantic relations for 1-hitter come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.