Whenever used in this article, the following terms shall have the following meanings, unless the context clearly indicates otherwise: (1) COMMISSION. The county commission with the judge of probate as chairman. (2) CHAIRMAN. The judge of probate acting as chairman of the county commission. (3) SUBDISTRICT. A drainage subdistrict. (4) ENGINEER. The agricultural engineer of the Alabama Extension Service. (Acts 1936, Ex. Sess., No. 127, p. 83, §2; Code 1940, T. 2, §263.)