A word used mainly in London by 'Roadmen' I know this because I am British (Help me I swear to god this country can suck my cock)
The word 'Pussio' is the same as calling someone a coward, a pussy, or a straight up bellend. It is mainly used to insult people even if they aren't doing anything 'cowardly'.
Roadman: "Oiiii, PUSSIO! Come here blud, why you sayin' you clapped my mumzy for fam?"