A suit was an item of clothing, usually consisting of at least a shirt, jacket and trousers. Alternatively, some women wore skirts in place of trousers.
The Tenth Doctor used to wear two main suits, a dark brown suit with blue pinstripes, (TV: The Christmas Invasion onwards) and a blue suit with red pinstripes. (TV: Smith and Jones onwards) For certain formal occasions, he would also don a tuxedo. (TV: Rise of the Cybermen, The Lazarus Experiment, Voyage of the Damned)
While on Earth, members of the Council of Dead wore identical pin-stripe suits and bowler hats to cover their horns. (PROSE: Snowfall, Attack of the Snowmen)
Bill B Brooks, an agent of Jason Dungeon, wore a suit with a flashy red and yellow tie when he met the Tenth Doctor. (PROSE: The Pictures of Emptiness)
Besnik Lucca, the most dangerous criminal in Cardiff in the early 21st century, always dressed in a crisp linen shirt and an Armani suit. (PROSE: SkyPoint)
June Turner, wore a dark grey skirt suit. (TV: Regeneration through Hound of the Korven)