Idiosyncratically is a word that means in a peculiar or distinctive manner. There are several synonyms that can be used instead of this word to convey similar meanings. Quirkily is one such word that denotes something that's done in a strange or unusual way. Eccentrically is another synonym that refers to someone who has unconventional or peculiar behavior. Oddly is also a word that can be used instead of idiosyncratically because it implies something that's different from what's expected or normal. Uniquely is a synonym that can be used to imply that something is exceptional or one-of-a-kind. All these words are synonyms for idiosyncratically and can be used interchangeably in sentences.