Alternatives to the noun 'dump' (as in "a data dump")

I see no reason to seek another word. Although this use of dump may be ‘non-standard’ in ordinary discourse, it appears to be ‘standard’ within the field in which your discourse will presumably take place. The fact that you cannot readily come up with a ‘better’ term suggests that ‘dump’ is in fact the best term.

Most of your audience will understand the term, and may be confused if you use a different one (“Hmm ... is he talking about something other than an ordinary data dump?”) If you are concerned that some of your audience may be novices or outsiders who will not understand the term, then it is courteous to provide a definition in a footnote or in parentheses; but the term should not be avoided. Those users are presumably seeking to learn about the field, and it is a disservice to them to use a non-standard term which they will not encounter in further reading.

The only other choice I can think of that fits in the place of dump is extract:

Here is a massive data extract from Globotech's ERP system. You'd think 20G would be a full extract, but this is actually just their bug description table.

May I suggest the following words, each appropriate depending on the context:

cache

depot

repository

emporium

warehouse

entrepot