腓

The calf of the leg (posterior lower leg). In medical or pathological contexts, it may mean "to wither" or "be ill," specifically referring to muscle atrophy or the wasting away of the calf.

Usually functions as a noun. Can function as a predicate in medical contexts meaning "to wither."

Frequently appears in tandem with 脛 (the shin/anterior lower leg) to describe the lower leg in its entirety.

The sense "avoid" is likely a phonetic loan for 避 (bì).

In texts concerning paralysis, aging, or disease, determine if the glyph is the subject (the calf) or the action (atrophying). If an anatomical reading creates a contextual impossibility, test for the loan meaning "avoid/shun."