Here are some synonyms for surreptitious:
* Covert
* Clandestine
* Secret
* Stealthy
* Underhanded
Here are some examples of how "surreptitious" can be used:
* "The journalist gained surreptitious access to the classified documents."
* "She gave him a surreptitious glance."
* "The spy was caught making a surreptitious phone call."
The word "surreptitious" often has a negative connotation, implying that something is being done in a sneaky or dishonest way.