The posterior, individually buttocks, colloquially referred to as one's bum, butt, or arse, was the backside of humanoid life forms, and many other bipeds or quadrupeds. As well as depositing bodily wastes and gasses, the buttocks were also a common focal point of sexuality.
The phrase 'kicking butt' was used in slang to describe besting an adversary. After successfully evading the surveillance of the Department with K9 Mark 2, Starkey announced that they had 'kicked surveillance butt'. In response, his robotic friend vowed to 'kick surveillance posterior' whenever possible from then on. (TV: The Korven)
While talking about men with Gwyneth, Rose Tyler said she liked a 'good smile' and a 'nice bum'. (TV: The Unquiet Dead) After psychografting herself into Rose's body, Cassandra O'Brien took great pleasure in examining her 'nice rear bumper', slowly stroking her newfound posterior with one hand. (TV: New Earth) Gwen Cooper complimented her boyfriend on his 'nice arse' while watching him get out of bed naked. (TV: End of Days) Minnie Hooper took the opportunity to squeeze the Tenth Doctor's bottom as he had a photograph taken with the Silver Cloak group, following it up by patting his basckside. (TV: The End of Time)
According to Susan Foreman's diary, Francis Minto shoved a protractor into Gillian Roberts's buttocks in mid-March 1963, and she destroyed her desk in rage. Mr Grange strapped her three times across the palm of her hand for vandalising school property. (PROSE: Time and Relative)
When Victor Kennedy absorbed Bliss, her face ended up on his right buttock. When Elton Pope asked where she was, Kennedy lifted himself up, farting as Bliss told him he didn't want to know. (TV: Love & Monsters)