Thingy

Suffering from post-regenerative amnesia, the Twelfth Doctor introduced Clara to the Paternoster Gang as "thingy" as he tried to recall her name. (TV: Deep Breath)

Whilst related a story concerning the Doctor's use of a teleport bracelet, Clara referred to the device as a "teleport thingy". (TV: The Witch's Familiar)

Behind the scenes
Although the Twelfth Doctor initially introduced her to the First Doctor as deceased, Clara explained that she was actually alive "thanks to the thingy swirling round the wotsit". In response, the Twelfth Doctor stated he "didna see that comin!". (NOTVALID: Doctor Whos?)