Chin

A chin was part of humanoid anatomy.

The Eleventh Doctor was remarked often for having a slightly large one, which got himself nicknamed (ironically by his previous self) "Chinny". (TV: The Day of the Doctor) Oswin Oswald said he could put an eye out with it, and called him "the chin". (TV: Asylum of the Daleks) The Twelfth Doctor later used the same term to describe his previous incarnation to Bill Potts. (COMIC: The Promise)

Cassandra O'Brien.Δ17 had her chin completely taken away. (TV: The End of the World)

Behind the scenes
The Tenth Doctor referred to him as "Chin" in NOTVALID: Cinema Introduction.