Definition of Base

(Chem.) The positive, or non-acid component of a salt; a substance which, combined with an acid, neutralizes the latter and forms a salt; -- applied also to the hydroxides of the positive elements or radicals, and to certain organic bodies resembling them in their property of forming salts with acids.
any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water;