Mo. Rev. Stat. § 506.200: Definitions.

1. The term "person" , as used in section 506.210, shall mean:

(1) The owner of the motor vehicle or trailer, whether it is being used and operated personally by said owner or by his agent;

(2) An agent using and operating the motor vehicle or trailer for his principal;

(3) Any person who is in charge of the motor vehicle or trailer and of the use and operation thereof with the express or implied consent of the owner.

2. The term "restricted, registered mail" means mail which carries on the face thereof in a conspicuous place, where it will not be obliterated, the endorsement, "deliver to addressee only", and which also requires a return receipt or a statement by the postal authorities that the addressee refused to receive and receipt for such mail.