Soundo
This is London slang for asleep.It derives from the phrase "sound asleep" thus "Soundo". I think it is probably unique to London and maybe South east London in particular.
I rang you this afternoon and you never answered the phone? No mate I was soundo!
Soundo
Sound. Cool.
Person 1 : yo bro you on your way ?
Person 2: aye bro I’ll be 10 minutes
Person 1: soundo
Person 2: aye bro I’ll be 10 minutes
Person 1: soundo