苹果皮 literally means 'apple skin' — a compound noun formed by combining 苹果 (píngguǒ, 'apple') and 皮 (pí, 'skin' or 'peel'). While 皮 can refer to the outer layer of many things (e.g., fruit, animals, or even abstract concepts like 'face'), in this context it specifically denotes the thin, edible outer covering of an apple. The word is commonly used in cooking, nutrition discussions, and everyday food preparation.

Apple peel is often highlighted for its dietary fiber and antioxidants, so 苹果皮 frequently appears in health-related contexts or when distinguishing between peeled and unpeeled apples. It’s a concrete, countable noun — you can say 一个苹果皮 (one apple peel), though more naturally, people refer to it collectively (e.g., 把苹果皮削掉, 'peel off the apple skin'). Unlike some other '–皮' compounds (e.g., 人皮, 'human skin'), 苹果皮 carries no figurative or sensitive connotations — it’s neutral and practical.