on the sly
US /ɑn ðə slaɪ/
UK /ɑn ðə slaɪ/
1.
en douce, en cachette, furtivement
doing something secretly or furtively
:
•
He was eating cookies on the sly when his mom wasn't looking.
Il mangeait des biscuits en douce quand sa mère ne regardait pas.
•
They were meeting on the sly to plan the surprise party.
Ils se rencontraient en douce pour organiser la fête surprise.
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