What is Ardent Spirit?

Legal Definition
Ardent spirits (ethyl alcohol), in alchemy, are those liquors obtained after repeated distillations from fermented vegetables. They are thus called because they will take fire and burn. Examples include brandy, spirits of wine, etc.
-- Wikipedia
Legal Definition
Spirituous or distilled liquors. Sarlls v. U. S., 152 U. S. 570, 14 Sup. Ct. 720, 38 In Ed. 556; U. S. v. Ellis (D. C.) 51 Fed. 808; State v. Townley, 18 N. J. Law, 311. This phrase, in a statute, does not include alcohol, which is not a liquor of any kind. State v. Martin, 34 Ark. 340.
-- Black's Law Dictionary