Green’s Dictionary of Slang

1. usu. in pl., faecal stains on one’s underwear; thus skid-marked adj.

1963–74		B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 25: Me old woman would have a stroke if she knew I’d passed out with skid marks on me Y-fronts.
1979		S. King Long Walk in Bachman Books (1995) 219: You got skidmarks in your underwear.
1988		R. Doyle Commitments 83: Jaysis, look at those skid marks.
1989		Eble Campus Sl. Sept. 6: scooter tracks – fecal matter left in underwear.
1996		P. Howard The Joy (2015) [ebook] Skidmark has the foulest rear end any of us has ever smelt.
1997		T. Winton Lockie Leonard, Legend (1998) 151: Those saggy undies with faint skidmarks.
2000		Observer Rev. 11 June 5: A dilapidated collection of skid-marked sheets.
2003		N. Griffiths Stump 195: All the trash in the gas we exhale [...] reduced to the skidmarks in ar unwashed kex.
2016		Eve. Standard (London) 10 Oct. 17/2: It will have implications for the culture long after Trump is — God willing — no more than a skidmark on history.
2017		T. Spicer Good Girl Stripped Bare 83: The Code of Ethics might as well be a piece of toilet paper as far as much of the media is concerned. And not even the soft stuff: the slippery shit that leaves skid marks.
2017		T. Pluck Bad Boy Boogie [ebook] ‘Those panties got skidmarks. You got shit on your uh, mouth’.

2. any form of bodily stain.

1999

Guardian G2 16 July 11: I changed to roll-ons. Apart from the skid marks they left on my T-shirt, they suited me fine.

3. (also skid) a general term of abuse.

2001		OnLine Dict. of Playground Sl. 🌐 skid, skidmark n. [...] An excessively stupid or unpleasant person.
2011		S. Kelman Pigeon English 135: Yeah, piss off, Skidmark!
2015		http://grey-magazine.com July 🌐 My lieutenant, a skidmark of a man, makes me deliver her personal effects to her family.

4. stains or smears of excrement in a lavatory bowl.

2012

J. Fagan Panopticon (2013) 107: The toilet pan has skid-marks, someone else’s shit.