The New Harvard Dictionary of Music says the bass range is E2 to C4, the soprano is C4 to A5, so I'd be surprised to hear a bass singing a note that was literally at a higher pitch than what a soprano was singing. It could happen with a bass and an alto, or a tenor and a soprano, as those ranges actually overlap.

I wonder whether what's meant is something like a soprano singing F4, say, while a bass is singing G3. G is a higher note than F, but the bass is in a lower octave – it might sound like a higher pitch, though it really isn't.

Anyway, sorry, but I don't know what, if any, musical term there is for this. I've heard the term "inversion" used in music, but for something very different; say there's a series of notes F-G-A-B somewhere in a piece of music, followed by B-A-G-F, the second series is an inversion of the first.