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)

The War Doctor made a habit of uttering "damn", usually as a sign of frustration or when things did not meet his satisfaction. (PROSE: Engines of War; AUDIO: Light the Flame, The Innocent, The Thousand Worlds, The Heart of the Battle, A Thing of Guile, The Neverwhen, Eye of Harmony, Pretty Lies, The Enigma Dimension)

The Eighth Doctor said 'Who the hell are you' to Lucie Miller when the Time Lords teleport her onto his TARDIS, (AUDIO: Blood of the Daleks) thinking she's Karen Coltraine. (AUDIO: Human Resources)

The Master swore the word 'damn' when during his child incarnation, (COMIC: The Organ Grinder) and when posing as Professor Yana. (TV: Utopia)

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)

Rose Tyler referred to Corin's profanity as "Donna swearing". (PROSE: The Turning of the Tide)

The First Doctor disliked swearing, chiding Susan Foreman and Bill Potts for their crude language. (TV: An Unearthly Child, Twice Upon a Time)

Rose Tyler once called Cassandra a "bitchy trampoline". (TV: The End of the World)

Behind the scenes
The Ninth Doctor's explanation about the TARDIS 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".