A bikini was an item of clothing.
Jo Grant wore a bikini when she went sunbathing. (PROSE: The Switching)
Whilst travelling to Florana, Sarah Jane Smith wore a bikini. (TV: Death to the Daleks)
Whilst visiting Lanzarote, Peri Brown wore a bikini. (TV: Planet of Fire)
The Eleventh Doctor swapped places with a stripper called Lucy who was to burst out of a cake for Rory Williams' stag night. After bursting out of the cake, he said that she was outside in a bikini and asked if someone could let her in and give her a jumper as she was a lovely girl and diabetic. (TV: The Vampires of Venice)
John Hart suggested "Bikini Cops" as an alternative name for Torchwood. (TV: Kiss Kiss, Bang Bang)
Simon Haldane bought a bikini for Troy Game to wear while sunbathing on his flat's patio. (PROSE: The Suns of Caresh)
Ace said that she had bikinis more respectable than the clothing Gilgamesh wanted her to wear. (PROSE: Timewyrm: Genesys)