heh, I did not mean to use those interchangeably in that statement.
but in general, I've heard different uses of the term, but usually some folks will make a point to use "film" for, I dunno, movies that should be considered fancier, or more serious than the status quo. Some take that seriously, others not so much. Plenty don't care. I really don't care.
Flick, though, has a couple of uses that I am aware of. It is either everything that isn't "film" (based on previous definition), simply another word for film (basically for anyone in the "does not care about 'film' fanciness" category), thus the same as movie, or, quite specifically: everything that is porn. And, more specifically, homemade porn.
...The porn thing was common among some of my high school buddies. I'm honestly not sure if social groups in other parts of the country have ever used flick for homemade porn, but I always assumed it was very common--now that I think about it, I feel that this use must have been around in some of those teen/sandler/spoof flicks or whatever that were rather common in the nineties. Or not.