Unsporting or underhand.
Unfaithful or adulterous.
The arrangement of people or items in a film so as to give the (false) impression that shots are taken from different angles in the same location.
An act of deception, fraud, trickery, imposture, imposition or infidelity.
Understaffed.
Done by moving the hand (and arm) from below.
Sly, dishonest, corrupt, cheating.
Insincere; sarcastic.
An underhanded compliment is actually criticism.
Secret; surreptitious.
His underhanded trick backfired and he was disqualified.
In an underhanded manner.
Devious people, collectively.