I. ˈən-dər-ˌhand adverb
Date: 1538
1.
a. : in a clandestine manner
b. archaic : in a quiet or unobtrusive manner
2. : with an underhand motion
bowl underhand
pitch underhand
II. adjective
Date: 1592
1. : underhanded
2. : done so as to evade notice
3. : made with the hand brought forward and up from below the shoulder level
an underhand serve