Webster's Revised Unabridged Dictionary · 1913

Underhand

Underhand (un"dẽr*hand`) , adjective

1.
Secret; clandestine; hence, mean; unfair; fraudulent. — Addison
2.
(Baseball, Cricket, etc.) Done, as pitching, with the hand lower than the shoulder, or, as bowling, with the hand lower than the elbow.

Underhand (un"dẽr*hand`) , adverb

1.
By secret means; in a clandestine manner; hence, by fraud; unfairly; dishonorably.
Such mean revenge, committed underhand. — Dryden
Baillie Macwheeble provided Janet, underhand, with meal for their maintenance. — Sir W. Scott

In modern usage, the sense is usually negative.

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.