Definition from Wiktionary, the free dictionary
- (idiomatic) Something ordinary or run-of-the-mill.
- The sandwich was plain old junk food, nothing special.
- (idiomatic) Nothing worth discussing; nothing that the speaker wants to mention.
- Often used as an evasion or conversation-stopper, when nosy queries are made. It can be an indirect way of telling someone to "mind his own business".