Weir \Weir\ (w[=e]r), Wear \Wear\,n. [OE. wer, AS. wer; akin to G. wehr, AS. werian to defend, protect, hinder, G. wehren, Goth. warjan; and perhaps to E. wary; or cf. Skr. v[.r] to check, hinder. [root]142. Cf. Garret.]

1. A dam in a river to stop and raise the water, for the purpose of conducting it to a mill, forming a fish pond, or the like.

2. A fence of stakes, brushwood, or the like, set in a stream, tideway, or inlet of the sea, for taking fish.

3. A long notch with a horizontal edge, as in the top of a vertical plate or plank, through which water flows, -- used in measuring the quantity of flowing water.

Source: Webster's Revised Unabridged Dictionary (1913)