Meanings of underhanded work in English

We suspect some underhanded work of Philip's which would be easy enough.

I'll play you a square game, and won't do any underhanded work.

I understand something of your underhanded work, Brown.

No more underhanded work, like we had before.

I scorn such underhanded work.

To dream of seeing disappointed children, denotes trouble from enemies, and anxious forebodings from underhanded work of seemingly friendly people.

Now, when you tell me about the missing plans, and you conclude that Andy is doing some underhanded work, I agree with you.

But some bureau chiefs still did as much underhanded work against the order as they dared, and it was often difficult to reach them.

"You said something about his underhanded work before," came from Sam.

"It's exactly like some of Link's underhanded work at Oak Hall," was Roger's comment.

"Low-down, underhanded work-doyou get what I mean?"