Cool

The Eleventh Doctor enjoyed denoting various things as cool, such as fezes, (TV: The Big Bang) stetsons (TV: Day of the Moon) and, most prominently, bow ties. (TV: The Eleventh Hour, The Snowmen) He told himself to "be cool" when making a first impression to Clara Oswald. (TV: The Bells of Saint John, The History of the Doctor)

The Twelfth Doctor cited the Eleventh Doctor's usage of the world "cool", among other reasons, as to why he held a low opinion of his predecessor. (COMIC: Terrorformer) During a Multi-Doctor Event, the Eleventh Doctor came to think of his successor as "very cool" if he had retained Clara as a companion. (COMIC: Four Doctors)