As used in this article, 1. "Building", in addition to its ordinary meaning, includes any structure, vehicle or watercraft used for overnight lodging of persons, or used by persons for carrying on business therein. Where a building consists of two or more units separately secured or occupied, each unit shall not be deemed a separate building.

2. "Motor vehicle", includes every vehicle operated or driven upon a public highway which is propelled by any power other than muscular power, except (a) electrically-driven invalid chairs being operated or driven by an invalid, (b) vehicles which run only upon rails or tracks, and (c) snowmobiles as defined in article forty-seven of the vehicle and traffic law.