Green’s Dictionary of Slang

1. (also yat) a young woman, a girlfriend; esp. derog., i.e. a promiscous woman, a prostitute.

2000		Taskforce ‘Red Light District’ 🎵 Like a cheap yatty on the corner.
2003		Dizzee Rascal ‘Wot U On?’ 🎵 Looking for your yat – she was sat next to me.
2015		67 ‘Live Corn’ 🎵 I was in the party flexing with a yat.
2021		Central Cee ‘Committment Issues’ 🎵 When I don't text back, I ain't with a yat, I'm in the bando, baby.

2. a cowardly man.

2003

UrbanDictionary.com 🌐 yatty [...] a coward.