A statue was a sculpture of a life-form, normally of its entire body.
A Melkur was an evil creature immobilised by the tranquil nature of Traken. Over time they turned into statues and disintegrated. The Master's TARDIS disguised itself as a Melkur as part of his plan to take over the Source. (TV: The Keeper of Traken)
The Fifth Doctor and Turlough visited the Corcovado statue in 21st century Rio de Janeiro. (AUDIO: Loups-Garoux)
The Weeping Angels, while being observed, looked like statues. (TV: Blink) The Statue of Liberty was turned into a Weeping Angel in 1938. (TV: The Angels Take Manhattan)