Spot on, BY. I said much the same thing privately to Slithy--I remembered after the fact that synecdoche covers several instances, and is in fact a bit of a subclass of metonymy, which can sometimes be confused with metaphor.

In retrospect, I think what I'm seeking would be the opposite of metonymy. When we say that using a whole to describe a part is an aspect of synecdoche, I believe there's an understanding that said part only exists as part of the whole, eg: in the daily bread example, we could refer to bread as food (whole for part), or food as bread (whole for part).

What I'm seeking is the term for referring to a part by focusing on one application of it (ie one whole to which it is a part) but indiscriminately applying said name to the part no matter how it's being used. To continue the bread example, we refer to money as bread, whether or not it's actually being used to purchase bread. Is this still synecdoche? Synedoche once-removed? Metonymic synecdoche (bread representing food is synecdoche + an aspect of money is its use for buying food--metonymy)? Or at this point does it become merely metaphoric?