a. 1. Secret; clandestine; hence, mean; unfair; fraudulent. Addison. [ 1913 Webster ]

2. (Baseball, Cricket, etc.) Done, as pitching, with the hand lower than the shoulder, or, as bowling, with the hand lower than the elbow. [ 1913 Webster ]

adv. 1. By secret means; in a clandestine manner; hence, by fraud; unfairly; dishonorably. [ 1913 Webster ]

Such mean revenge, committed underhand. Dryden. [ 1913 Webster ]

Baillie Macwheeble provided Janet, underhand, with meal for their maintenance. Sir W. Scott. [ 1913 Webster ]

In modern usage, the sense is usually negative. [ PJC ]

2. (Baseball, Cricket, etc.) In an underhand manner; thrown with the hand no higher than the shoulder and the palm turned upward during part of the pitch; -- said of pitching or bowling a ball. [ 1913 Webster +PJC ]

a. 1. Underhand; clandestine. [ 1913 Webster ]

2. Insufficiently provided with hands or workers; short-handed; sparsely populated; obsolete in this sense, short-handed or understaffed being the preferrred term. [ 1913 Webster +JG ]

Norway . . . might defy the world, . . . but it is much underhanded now. Coleridge. [ 1913 Webster ]

adv. In an underhand manner. [ 1913 Webster ]