Swearing

Swearing was the use of speech considered rude.

The Ninth Doctor once mentioned that the TARDIS' translation circuit had a swear filter that prevented the passengers from hearing any swear words; even an angry cavewoman's rants were translated as her saying, "Blinking", rather than a more apt phrase. (PROSE: Only Human)

News broadcasts would sometimes censor swear words in their footage, bleeping them out with sound effects. (AUDIO: Outbreak)

Jack Harkness chided Gwen Cooper for her language when she called him a bastard. (TV: Everything Changes)

The Malmooth Chantho respectively began and ended her sentences with "chan" and "tho"; as she explained to Martha Jones, to not do so would be akin to swearing. When Martha requested that she swear just once, Chantho complied by saying "no". (TV: Utopia)

"Pacifism" was a swear word for Sontarans. (AUDIO: The Eternal Battle)

Yasmin Kahn's grandfather often swore loudly in Punjabi when he accidentally injured himself. He hoped that his young granddaughter hadn't understood, but she had. (AUDIO: Fallout)

The Twelfth Doctor's internalised anger sometimes lead to a preponderance of swear words appearing on the psychic paper. (TV: Dark Water)

The Eleventh Doctor, on the other hand, was prone even to chastise horses for their foul language. (PROSE: Houdini and The Space Cuckoos)

In a parallel universe, a Time Lord chided a colleague for his language when he reacted to news of the Doctor's escape with the exclamation "Oh, shit!" (AUDIO: Exile)

Behind the scenes
The Ninth Doctor's explanation about the TARDUS translation systems is a reference to the lack of swearing in televised Doctor Who, which has remained a family programme since its inception. Indeed, William Hartnell, who played the First Doctor, specified that the show had "no sex or swearing" in a 1964 interview. (REF: The First Doctor Handbook)

The BBC Wales series sometimes teases at swearing, cutting it close in editing for humour. One 2017 episode, Thin Ice, cheekily cuts away as Bill utters: "No sh—". Back in 2006, New Earth cuts from Cassandra calling Rose Tyler "that little—" to Rose saying, "bit rich".