uncharacteristically
UK: ˌʌn.kær.ək.təˈrɪs.tɪ.kli | US: ˌʌn.ker.ək.təˈrɪs.tɪ.kli
adv. in a manner that is not typical or usual for someone or something
The word is built from the negative prefix "un-" (Old English "un-", meaning "not") attached to "characteristic," which derives from "character" (Latin "character," meaning "mark or distinctive quality") + the adjectival suffix "-istic" (Greek "-istikos"). The adverbial suffix "-ally" (Latin "-aliter") is then added to form the adverb. The progression reflects a logical negation of typical behavior, emphasizing deviation from expected traits.
She uncharacteristically arrived late to the meeting.
He was uncharacteristically quiet during the debate.
The cat behaved uncharacteristically, ignoring its favorite toy.
The CEO spoke uncharacteristically softly at the press conference.
The weather turned uncharacteristically cold for May.