Okla. Stat. tit. 47, § 1-135
Every motor vehicle having a seat or saddle for the use of the rider and designed to travel on not more than three wheels in contact with the ground, but excluding a tractor or a motorized bicycle.
Laws 1961, HB 556, p. 318, § 1-135, eff. September 1, 1961; Amended by Laws 1978, SB 521, c. 304, § 2.