What does 皮肤 (pí fū) mean in English?

Card 310HSK 2010 Level 4310/586
CARD310
PROGRESS53%
皮肤
皮膚
pí fū
skin; CL:種|种[zhong3]

Reveal: Click/Space/Enter/↑↓/w/s/j/kNavigate: ←→/h/l/a/d