Md. Code, Transportation § 11–158

(a) “Semitrailer” means, except as provided in subsection (b) of this section, a vehicle that:

(1) Has no motive power;

(2) Is designed to carry people or property and to be towed by a motor vehicle; and

(3) Is constructed so that some of its weight and load rests on or is carried by another vehicle.

(b) “Semitrailer” does not include a pole trailer.