Green’s Dictionary of Slang

to expel faecal matter unintentionally when breaking wind, thus n. the sharts.

2011		G. Hayward Corruption Officer [ebook] Ch. 1: I am over here sharting on myself, like when you think you have to fart but mistakenly shit on yourself instead.
2016		T. Robinson Rough Trade [ebook] Junior looked at me like I’d sharted my Sunday pants right in the middle of Communion.
2017		T. Spicer Good Girl Stripped Bare 120: I have a case of the ‘shomits’, a human fountain flowing from both ends (It’s a step up from the ‘sharts’).