Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unco is an adverb meaning "to a remarkable degree or extent". It carries one recorded sense.
to a remarkable degree or extent
“she was unusually tall”
“Notably missing from the network's fall line-up are any half-hour scripted comedies”
Definitions, synonyms and semantic relations for unco come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.