Landspout

A landspout is a term coined by meteorologist Howard B. Bluestein in 1985 for a kind of tornado not associated with the mesocyclone of a thunderstorm. The Glossary of Meteorology defines a landspout as

Landspouts form during the growth stage of convective clouds by stretching boundary layer vorticity upward and into the cumuliform tower's updraft. They generally are smaller and weaker than supercellular tornadoes and do not contain a mesocyclone or pre-existing rotation in the cloud. Because of this, landspouts are rarely detected by Doppler weather radar.