Sometimes the identity of old mate may not be discernable from the message's context. Quite often in such instances the identity is immaterial to the underlying message.
Person two: "You have to stop fucking her, seriously."
Person one: "Old mate dropped by and we watched the cricket for a bit."
Person two: "McGrath had a shocker, hey...."
Used to describe a person (not present) who you do not know very well, have not known very long and is therefore not your really your mate, but you do have some sort of general interaction with.
Did you see old mate nearly trip over ?
Can you believe old mate pulling his car in front of mine like that !
2. Name for a drug source you do not wish to reveal.
3. Word to describe a perfect stranger (male) when saying something funny about them.
2. "I got this gram from my old mate."
3. "Check out that old mate's mullet"