1 loaf of bread
Commonly used when buying a whole loaf of bread at a bakery. The weight is approximately 1 kin (600 g), but the term focuses on the loaf as a unit.
パン屋で一斤の食パンを買った。
I bought a loaf of bread at the bakery.
From 一 (one) + 斤 (kin, a traditional unit of weight). The bread sense comes from the typical weight of a standard loaf.