Mikkel wrote:"π is only half a pie." I think that was a pun, really.
hmm, you raise a good point, and in a relaxed scenario, such as a party, or, while drinking at a pub, I'd probably go along with it, but by a more strict definition I'd probably call it just a generic clever play on words, as technically speaking you're neither substituting words, nor using a homonym instead of a synonym.