pain n1 : punishment
2 a : physical discomfort associated with bodily disorder (as disease or injury)
b : acute mental or emotional suffering
on pain of
un·der pain of
: subject to penalty or punishment of [ordered not to leave the country on pain of death]
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.