Matt Cutts, in a comment on his blog, explains the differences between the Google terminology "data push" vs. "data refresh". Of course, we really don't get a clue as to what either of them actually is...but well, I'll let you read it for yourself.
A data push is a superset of a data refresh (that is, a data refresh is an instance of a data push). Typically a data refresh is something with a well-established history, e.g. we have automatic tests in place and the data to be sent out is sent out automatically (assuming that all the automatic sanity checks pass). A data push may tend to be less automated and thus may undergo more evaluation. But the terms are often used interchangeably by Googlers, because we know what we mean, so you're pressing for a pretty fine connotation.
So, there you go. Now you can throw both of those terms out freely, and unlike the Googlers, you WON'T know what you mean. LOL.
Added: Just to make sure everyone has all the info on this terminology, I refer you to Rebecca's notes on the Matt Cutts video where he attempted to further define a data center (based on a question I asked him), in which he said:
The smallest change is called a data refresh, and that's essentially you're changing the input to the algorithm, you're changing the data that the algorithm works on.