What is Sewer?

Legal Definition
Properly a trench artificially made for the purpose of carrying water into the sea, river, or some other place of reception. Public sewers are, in general, made at the public expense. Crabb, R. P. §113.
-- Bouviers Law Dictionary
Legal Definition
A fresh-water trench or little river, encompassed with banks on both sides, to drain off surplus water into the sea. Cowell. Properly, a trench artificially made for the purpose of carrying water into the sea, (or a river or pond.) Crabb, Real Prop. § 113. In its modern and more usual sense, a "sewer" means an under-ground or covered channel used for the drainage of two or more Separate buildings, as opposed to a "drain," which is a channel used for carrying off the drainage of one building or set of buildings in one curtilage. Sweet. See Valparaiso v; Parker, 148 Ind. 379, 47 N. E. 330; Fuchs v. St. Louis, 167 Mo. 620, 67 S. W. 610, 57 L. R. A. 136; State Board of Health v. Jersey City, 55 N. J. Eq. 116, 36 Atl. 835; Aldrich v. Paine, 106 Iowa, 461, 76 N. W. 812. See Commissioners of sewers.
-- Black's Law Dictionary