F*ck

F*ck was a profane word, sometimes used as a synonym for sex.

The word was used in the expressions "what the f*ck?" (TV: Everything Changes, Countrycide) and "f*ck knows", (TV: Random Shoes, End of Days) and the terms "f*cker" (TV: Countrycide) and "f*ck buddy". (TV: Out of Time)

Specific usages
Ianto once screamed, "Show some f*cking mercy!" while Lisa was getting attacked by the Pterodactyl Myfanwy. (TV: Cyberwoman)

Gwen Cooper once shouted, "F*ck you!" at Jack Harkness after he taunted her for her affair with Owen Harper. (TV: End of Days)

Owen used the word to call a group of cannibals "sick f*ckers". (TV: Countrycide) He also used "F*ck knows" in response to a question about Eugene Jones. (TV: Random Shoes)

Rhys Williams once in a fit of rage told Gwen to, "sit the f*ck down!" (TV: Combat) He also used the word when, facing a hostile Nostrovite in the form of his mother, Brenda Williams, he exclaimed "F*ck!" when the chainsaw he wielded failed to work. (TV: Something Borrowed)

Upon discovering a bomb, Allen Shapiro gave his last words, "Oh, f*ck!", immediately before being caught in its explosion. (TV: The Blood Line)

When Martyn told Gwen Cooper that he was offended by her use of the word "chav", she told him to f*ck off. (AUDIO: Smashed)

Kaitlin Russell once told Rhys that he could, "f*ck right off", not believing his claims of alien involvement. (AUDIO: Sargasso)

In one of Panda's fake realities, he was a chef on the show, ''What The F**k Do You Call That?. ''He also repeatedly said "f*ck", "f*cking", and many other variations and combinations. (PROSE: Framed)

Bernice Summerfield thought "that maybe time travel f*cks with your mind". Roberta once said "f*ck off" to a catfood monster. Zamina thought that Roberta would have put how far you can twist the patterns of life down to “accumulated karma, just another way in which the fates conspire to f*ck you up”. Lambada once said “Those f*cks at KGB won't say much but they did confirm that a classified number of passengers got greased on the outbound Central Line platforms.” In response to dogface asking “What about the real world?”. Lambada also said “Christ in a bucket, The f*cking V Soc. Like we don't have enough troubles. Old Sam at one point said that the soldiers didn’t put “f*cking spines” on their armour. Dogface asked Blondie if he had “never seen two trains f*cking before?” when the gateway compensator prevented matter-annihilation from taking place saving Los Angeles, but caused the physical substance of two trains to become smoothly integrated as they emerged from the tunnel gateway and some passengers immediately died. Ming told Credit Card that “You shouldn't have spent twenty years making yourself f*cking indispensable then, should you?” In response to him needing a rest. Benny once stated that she is “taken over by a f*cking alien intelligence, why do you think?" in response to the Doctor asking her why she wants to shoot him. A dogface drone once said that there was a “f*cking battalion in the galleria”. Dogface once said “I think someones f*cking with our signaling”. Ming used the expression “f*ck no”, and later used the expression “What the f*ck are you doing?”. Lambada once said “What the f*ck was that?” (PROSE: Transit)

Christine LaFayette once said “F*ck you, mother, f*ck you to hell and back.” (PROSE: Lucifer Rising)

Behind the scenes
Before his casting as the Twelfth Doctor, Peter Capaldi was well known for portraying the character Malcolm Tucker in The Thick of It, who commonly used the word. This led to some fans joking that the Doctor would say f*ck at some point in the series.

After the broadcast of Let's Kill Hitler, some viewers complained, believing that a Nazi guard said, "Where the f*ck is he?" In reality, the guard said, "Was machen sie?", which translates to, "Stop, what are you doing?" in English.