Oh yeah, you're right, Go Punk! It could also mean "or". But it isn't used very often, is it? Since he said math, I was thinking less of logic/discrete math. Not many books use || for "or". U or V is more common.
Actually, now I remember. It's the programming source code that people use || for "or". For most math books and logic books I'm familiar with, "U" or "V" is used to denote "or".