Brad \Brad\, n. [Cf.OE. brod, Dan. braad prick, sting, brodde ice spur, frost nail, Sw. brodd frost nail, Icel. broddr any pointed piece of iron or stell; akin to AS. brord point, spire of grass, and perh. to E. bristle. See Bristle, n.]

A thin nail, usually small, with a slight projection at the top on one side instead of a head; also, a small wire nail, with a flat circular head; sometimes, a small, tapering, square-bodied finishing nail, with a countersunk head.

Source: Webster's Revised Unabridged Dictionary (1913)