A jumper was an item of clothing, often worn over a shirt, made of knitted wool.
The Fifth Doctor wore two similar cricketing jumpers under his two beige coats. (TV: Castrovalva onwards, The Awakening onwards) Similarly, the Seventh Doctor wore a sleeveless pullover, covered in turquoise zig zags and red question marks, (TV: Time and the Rani onwards) whilst the Twelfth Doctor wore a jumper patterned with holes. (TV: Listen et al) The Ninth Doctor dressed almost exclusively in long sleeve V neck jumpers, worn underneath his leather jacket. (TV: Rose onwards)
While visiting Fang Rock, Leela wore a grey jumper. (TV: Horror of Fang Rock)