weir

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A fence or wattle placed in a stream to catch or retain fish.
2. n. A dam placed across a river or canal to raise or divert the water, as for a millrace, or to regulate or measure the flow.

Century Dictionary and Cyclopedia

1. n. A dam erected across a river to stop and raise the water, as for the purpose of taking fish, of conveying a stream to a mill, of maintaining the water at the level required for navigating it, or for purposes of irrigation.
2. n. A fence, as of twigs or stakes, set in a stream for catching fish. Weirs differ from pounds principally in being constructed, in whole or in part, of brush or of narrow boards, with or without netting; and they are sometimes arranged so that at low tide a sandbar cuts off the escape of the fish, leaving them in a basin, and allowing them to be taken at any time before a certain stage of rise of the next tide. Weirs are of two kinds, the shoal-water weir and the deep-water weir. The shoal-water weir, as illustrated in fig. 1, has a leader L, which is a row of stakes, generally woven with brush, leading out from the shore. Its extremity is at the entrance of the big pound M. The big pound is likewise of stakes filled with brush, and its entrance 30 feet wide. This leads by a passage 5 feet wide into the little pound N, and this into the pocket O, which is a frame about 16 feet long and 10 feet wide, with sides of netting, and a board floor. The fish following the shore meet the leader, turn and follow it into the big pound; here they follow the side around until they pass into the little pound, and from that into the pocket, where they are left by the receding tide and taken out at low water. The deep-water weir (fig. 2) has a similar leader A, extending to the entrance of the big pound, or heart, B, beyond which are the small pound C and the bowl D, into which the fish finally go. The form of the inclosures in both cases leads the fish constantly forward, and they rarely or never find their way back through the passages. In both figures E represents the land or high-water mark, and F the low-water mark.

Wiktionary

1. n. an adjustable dam placed across a river to regulate the flow of water downstream
2. n. a fence placed across a river to catch fish

GNU Webster's 1913

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

WordNet 3.0

1. n. a low dam built across a stream to raise its level or divert its flow
2. n. a fence or wattle built across a stream to catch or retain fish