con ‧ spi ‧ ra ‧ to ‧ ri ‧ al /kənˌspɪrəˈtɔːriəl/ BrE AmE adjective
1 . a conspiratorial expression, voice, or manner suggests you are sharing a secret with someone:
His voice became low and conspiratorial.
Pat whispered to Maggie in a conspiratorial tone.
conspiratorial whisper/smile/wink etc
Britta gave him a conspiratorial smile.
2 . relating to a conspiracy
—conspiratorially adverb