noun
round meat; pork thigh meat
Specifically refers to meat from a pig's thigh, the cut used for making ham. A specialized butchery term.
このハムは良質の髀肉から作られています。
This ham is made from high-quality pork thigh meat.
もも肉 is the common everyday word for thigh meat (chicken, pork, etc.), while 髀肉 is a specialized term for pork thigh meat used in ham production.
The kanji 髀 means 'thigh' or 'femur', and 肉 means 'meat'. The reading ひにく is the on'yomi of the characters. The variant 脾肉 uses 脾 ('spleen'), likely a phonetic or historical variant; the exact derivation is uncertain.