As used in this chapter–

(a) The term “interstate commerce” means commerce between any State, Territory, possession of the United States, or the District of Columbia, and any place outside thereof.

(b) The term “switchblade knife” means any knife having a blade which opens automatically–

(1) by hand pressure applied to a button or other device in the handle of the knife, or

(2) by operation of inertia, gravity, or both.