usage: marked by deception; "achieved success in business only by underhand methods"
1. underhandedly, underhand
usage: slyly and secretly; "Mean revenge, committed underhand"- John Donne; "oldline aristocratic diplomats underhandedly undermined the attempt...to align Germany with the Western democracies"- C.G.Bowers
2. underarm, underhand
usage: with the hand swung below shoulder level; "throwing a ball underarm"