Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
underhandedly is an adverb meaning "slyly and secretly". It carries one recorded sense.
slyly and secretly
“Mean revenge, committed underhand”
“oldline aristocratic diplomats underhandedly undermined the attempt...to align Germany with the Western democracies”
Definitions, synonyms and semantic relations for underhandedly come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.