self-inflicted pain; hurting oneself (to deceive an opponent)
Rarely used alone; almost exclusively appears in the idiom 苦肉の策 (a desperate measure born of self-sacrifice or a painful choice). The literal sense of 'hurting oneself to trick an adversary' is historical/strategic.
See also: 苦肉の策
The phrase 苦肉の策 refers to a painful measure in which one would even hurt oneself to deceive the opponent.
stratagem of sowing discord in the enemy camp through sedition
An abbreviation of 苦肉の計, corresponding to Chinese 苦肉計, a stratagem in which one undergoes real injury or hardship to deceive an opponent.