Green’s Dictionary of Slang

1. (US) as an intensifier, exceedingly.

1907

W.M. Raine Bucky O’Connor (1910) 217: That round-bellied Papago pony in front belongs to Sheriff Forbes, or I’m away wrong.

2. (Aus.) in a sexual context, outside a primary relationship, adulterously, i.e. ‘away from home’.

2000

R.G. Barrett Leaving Bondi (2013) [ebook] Les got the distinct feeling that Digger was having it away.