What is Boom?

Legal Definition
An enclosure formed upon the surface of a stream or other body of water, by means of piers and a chain of spars, for the purpose of collecting or storing logs or timber. Powers' Appeal, 125 Pa. 175, 17 Atl. 254, 11 Am. St. Rep. 882; Lumber Co., v. Green, 76 Mich. 320, 43 N. W. 576; Gasper v. Heimbach, 59 Minn. 102, 60 N. W. 1080; Boom Co.rp. v. Whiting, 29 Me. 123.
-- Black's Law Dictionary