Definition from Wiktionary, the free dictionary
mesovortex (plural mesovortices)
- A small scale, vertical vortex of air associated with a thunderstorm that occurs at less than one kilometer from the ground and is between 2-20 kilometers in width.
Derived terms 
- Trapp, R.J., and M.L. Weisman, 2003: Low-Level Mesovortices within Squall Lines and Bow Echoes. Part II: Their Genesis and Implications. Mon. Wea. Rev., 131, 2804–2823.