underhand

Executed with the hand brought forward and up from below the level of the shoulder; underarm.

Dishonest and sneaky; underhanded.

With an underhand movement.

In a sly and secret way.

By secret means; in a clandestine manner, and often with an evil design.

By fraud; by fraudulent means.

Secret; clandestine: usually implying meanness or fraud, or both.

Sly; contriving; deceitful.

Performed or done with the knuckles of the hand turned under, the palm upward, and the thumb turned from the body: as, underhand bowling in cricket.

Secret; clandestine; hence, mean; unfair; fraudulent.