secretly Synonyms

on the qt in secret in one's heart surreptitiously secretively discreetly conspiratorially inconspicuously clandestinely behind closed doors in private in one's mind sub-rosa backstage deep down in camera in confidence off the record behind back by stealth unofficially unobtrusively unobserved under the counter under cover undercover sneakily on the sly on the side on the quiet on the q.t. at heart underhandedly underground inside inly indistinctly indefinably indecisively incognito hazily furtively duskily deducibly deceitfully cryptically covertly confidentially instinctively internally