on the sly

1. 1.

   in a furtive manner

   “the soldiers were furtively crawling through the night”

   Synonymsfurtively

Questions about on the sly

What does on the sly mean?

on the sly means "in a furtive manner".

What is another word for on the sly?

Close synonyms include furtively. Each sense on this page lists its own synonyms, because a word with several meanings rarely has one substitute that works for all of them.

Is on the sly a common word?

on the sly is banded "Rare" — specialist or archaic — most readers will not have met it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.