For the purpose of this subchapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
   ALL TERRAIN VEHICLE or ATV or UNLICENSED MOTOR VEHICLE or UMV.  Any motorized trail bike, minibike, two-, three-, four- or six-wheel motor vehicle not licensed for travel on any public street or highway pursuant to the provisions of M.S. Chapters 168, 169 and 171 as they may be amended from time to time. Prima facie evidence of such vehicle being unlicensed shall be the absence of any license plate being displayed upon the vehicle as required by law.
(1990 Code, § 1006.010)