confidentially Synonyms

between us on the q.t. off the record in confidence in camera surreptitiously secretively discreetly conspiratorially collusively clandestinely between ourselves behind someone's back behind closed doors on the qt on the quiet on the side unofficially unobtrusively unobserved under the counter under cover unconstitutionally unbeknownst unattainably trustfully thievishly undercover sneakily on the sly in private in secret ourselves inwardly intimately informally indoors hiddenly furtively familiarly esoterically covertly confidential confidence closely parentally personally private mystically sub-rosa