Synonyms of on the sly in English:

on the sly


See definition of on the sly

phrase

1‘is she meeting some other guy on the sly?’

SYNONYMS
in secret, secretly, furtively, stealthily, sneakily, slyly, surreptitiously, covertly, clandestinely, on the quiet, on the side, behind someone's back, under cover
under the counter
informal on the q.t.
ANTONYMS

openly