surreptitious

Others find decoys to place in their pouches, pocketing their real devices for surreptitious use throughout the school day.

A sheriff’s jail supervisor testified that Baker also tried to leave coded kites — a surreptitious method of inmate communication using handwritten binary code on paper — in a courthouse stairwell that the widow used after him.

After the couple found out about her surreptitious sterilization, “All our plans came tumbling down.”

It was suggested it had been conducted by the UK to be able to blame Russia "as part of a sort of bizarre and surreptitious intelligence operation of some variety", he added.

For the defense, the government’s surreptitious recordings were hard to overcome.