not open and aboveboard; secret and crafty or dishonorable

an underhand deal with the chief of police.

executed with the hand below the level of the shoulder and the palm turned upward and forward

an underhand delivery of a ball.

with the hand below the level of the shoulder and the palm turned upward and forward

to bowl underhand.

secretly; stealthily; slyly.

adjective

aboveboard , forthright , frank , honest

adjective

clandestine , concealed , crafty , crooked , cunning , deceptive , devious , dirty-dealing , dishonest , dishonorable , double-crossing , duplicitous , fraudulent , furtive , guileful , hush-hush * , indirect , insidious , oblique , on the qt , on the quiet , secret , secretive , shady , shifty , slippery * , sly * , sneaking , sneaky , stealthy , sub-rosa , surreptitious , treacherous , tricky , two-faced * , two-timing , undercover , underhanded , under wraps * , unethical , unfair , unjust , unscrupulous , wily , disingenuous , lubricious , chicane , covert , deceitful , machiavellian , sinister