Wiktionary
n. 1 (context colloquial Australia English) An elderly man. 2 (context colloquial Australia English) In general, any person, whose specific identity can be deduced from context.
Usage examples of "old mate".
The police sergeant is an old mate of Big Jack's and says Bozo should come along anyway and spar, that if he's that good the experts will probably want to take a look at him for the future.
His old mate Kevin Brown, now with the Drug Enforcement Agency, lives near the airport, so Nick decides to drop in.
Whether it actually pays you to desert depends on whether you can count on your old mate to finish rearing the kids, and whether you are then likely to find a receptive new mate.
When the hard-bitten old mate walked over and put his hand against the coffeepot sitting on one burner of the primus stove, it was slightly warm to the touch.