If you mean slang as in internet slang, then it means "Certified Old Fart".
Garrett mean in cockney slang
the peak
Slang is slang It's the s' "LANG " uage.
In old slang, milkshake mean butt.
It is slang for having sex.
he means what does being a sponge mean in slang
Dough is a slang word for money.
Cool itself, unless you are using it to mean mildly cold, is a slang word. Just because it is old slang doesn't mean that it is not still slang.
peak - peak.
''Dill'' means ''idiot'' as australian slang.
It is slang for bowel movement