Of a thing: done with evasive or guilty secrecy.
Of a thing: that has been acquired by theft; stolen; also (generally) taken stealthily.
Of a person or an animal: sly, stealthy.
Of a person, etc.: inclined to steal; pilfering, thieving.
Secret; surreptitious.
Done by moving the hand (and arm) from below.
Sly, dishonest, corrupt, cheating.
Insincere; sarcastic.
An underhanded compliment is actually criticism.
His underhanded trick backfired and he was disqualified.
Understaffed.
In an underhanded manner.
Devious people, collectively.