Yes, it must extend from cloud base to the ground.
In North America a swirling column of sand is called a dust devil. It resembles a tornado in appearance but does not extend to a cloud base and the winds are not nearly as strong.
Tornado
A violently rotating column of air is called a tornado.
It is a tornado.
A rotating cone shaped column of air extending downward from a cloud when it touches the ground it is called a tornado
Correct, it is a tornado.
tornado
A tornado is a vortex and may also contain vortices. A vortex is a rotating body of liquid or gass. In a tornado, the vortex is made visible by condensation or dust and debris. It may look like a cone, tapering appendage, or column attatched to the clouds, or may take the appearance of a tube or swirling mass of dust.
A rotating column of air is known as a whirlwind. If it is violent and connects to both the ground and the cloud base of a thunderstorm, it is considered a tornado.
A tornado usually forms from a large column of rotating air called a mesocyclone. A tornado therefore has quite a bit of angular momentum, so air spirals into the it.
A tornado made of air is a tornado. Part of the definition of a tornado is "a violently rotating column of air."
This is called a waterspout