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)
Lady Peinforte sculpted a statue called Nemesis out of validium in 1638. (TV: Silver Nemesis)
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)
A giant statue of a human was carved out of gregarian rock on the Ark during its 700-year journey to Refusis II, but was given a Monoid head when they took over. Monoid One had a nuclear bomb planted in the statue's head to destroy the Ark and the human passengers, but it was thrown out of the launching bay by a Refusian. (TV: The Ark)