a localized

tornado -- a localized and violently destructive windstorm occurring over land characterized by a funnel-shaped cloud extending toward the ground.

I think (over land ------- above the land) Is it right?

Could anyone explain the higlighted words?

You are right about "over land" , it means "above land". "Localized" means it is restricted to a certain area and does not cover a large territory. As for funnel-shaped, have a look at a funnel http://inst.sfcc.edu/chemscape/catofp/mixpour/sepfunl/pic/121846st.jpg and then compare that with tornado http://zero.navi.cx/gallery/d/7483-2/funnel.png

Localized here means it occurs in a relatively small space or locale. Tornadoes do not cover large areas the way other weather phenomena (e.g., storms, fronts) do.

You are right about over land. Here it means tornadoes occur over the land as opposed to over the sea. I believe in the sea they are called waterspouts.

This is a funnel. Compare its shape to that of a tornado. 👁 Smile :)