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on the sly

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on the sly

Fig. secretly and deceptively. She was stealing little bits of money on the sly. Martin was having an affair with the maid on the sly.

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on the sly

secretly She's been going out with him on the sly.

See also: on, sly

on the sly

Furtively, secretly, as in She's always eating cookies on the sly. The adjective sly, which means "cunning" or "crafty," is here used as a noun. [c. 1800]

See also: on, sly

on the sly

mod. secretly and deceptively. She was stealing little bits of money on the sly.

See also: on, sly

on the sly

In a way intended to escape notice: took extra payments on the sly.

See also: on, sly