A storehouse (Deuteronomy 28:8; Job 39:12; Haggai 2:19) for grain, which was usually under ground, although also sometimes above ground (Luke 12:18).

Noah Webster's New International Dictionary of the English Language

1. (n.) A covered building used chiefly for storing grain, hay, and other productions of a farm. In the United States a part of the barn is often used for stables.

2. (v. t.) To lay up in a barn.

3. (n.) A child. [Obs.] See Bairn.