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