adj. & n.
adj. 1 chief in size, importance, extent, etc.; principal (the main part; the main point). 2 exerted to the full (by main force).
n. 1 a principal channel, duct, etc., for water, sewage, etc. (water main). 2 (usu. in pl.; prec. by the) a the central distribution network for electricity, gas, water, etc. b a domestic electricity supply as distinct from batteries. 3 archaic or poet. a the ocean or oceans (the Spanish Main). b the mainland. in the main for the most part. main brace Naut. the brace attached to the main yard. the main chance one's own interests. main course 1 the chief course of a meal. 2 Naut. the mainsail. main deck Naut. 1 the deck below the spar-deck in a man-of-war. 2 the upper deck between the poop and the forecastle in a merchantman. main line 1 a chief railway line. 2 sl. a principal vein, esp. as a site for a drug injection (cf. MAINLINE). 3 US a chief road or street. main stem US colloq. = main street. main street the principal street of a town. Main Street US materialistic philosophy (after Sinclair Lewis's novel, 1920). main yard Naut. the yard on which the mainsail is extended. with might and main with all one's force.
[ ME, partly f. ON megenn, megn (adj.), partly f. OE mgen- f. Gmc: (n.) orig. = physical force ]