Mich. Comp. Laws § 247.331

Sec. 1. As used in this act: (1) "Advertisement" means any writing, printing, picture, painting, display, emblem, drawing, sign or similar device which is posted or displayed outdoors on real property and is intended to invite or to draw the attention or to solicit the patronage or support of the public to any goods, merchandise, property, real or personal, business, services, entertainment or amusement, manufactured, produced, bought, sold, conducted, furnished or dealt in by any person or for any political party or for the candidacy of any individual for any nomination or office; and the term shall also include any part of an advertisement recognizable as such. (2) "Bus passenger shelter" means any rigid structure situated upon or attached to real property outdoors, primarily or principally for the purpose of furnishing a waiting room or shelter for the use and convenience of the passengers of common motor carriers, but suitable for the purpose of furnishing a background, base or support upon which an advertisement may be posted. (3) "Highway" means every way or place of whatever nature open to the use of the public for purposes of vehicular travel in this state. (4) "Municipality" means any city or incorporated village. (5) "Post" means post, display, print, paint, burn, nail, paste or otherwise attach. (6) "Real property" means any property physically attached or annexed to real estate in any manner whatsoever.