Green’s Dictionary of Slang

grot n.

1. a dirty, untidy person.

1967–8		Baker et al. CUSS 130: Grot An obnoxious person.
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 63: GROT — A person who doesn’t bother to wash regularly or take care with personal hygiene.
1998		A. Warner Sopranos 120: ‘It’s Henry!’ [...] ‘It’s a fucking ancient old ugly grot that’s what’.

2. dirt, detritus.

1984		‘Derek Raymond’ He Died with His Eyes Open 123: You stink with the grot of that Staniland case.
1992		K. Lette Llama Parlour 47: Instead of an orgy of grot and grime she led me into a spotlessly clean room.
1999		Guardian G2 21 June 12: This higgeldy-piggeldy mix of grace and grot.
2007		S. Maloney Sucked In 161: He wore [...] a grot-marinated gabardine raincoat.
2012		(con. 1980s) I. Welsh Skagboys 113: The hotel [...] wis an Algerian grot-hole.
2019		C. Hammer Silver [ebook] Compared to his Corolla, it’s grot-free.

In derivatives

grotbag (n.)

a repellent individual.

2018

I. Welsh Dead Man’s Trousers [40]: I was almost even tempted to call Syme to pull a favour, but I’m staying away from that grotbag.