I thought a dyno is a mechanism that a standalone engine can be rigged up to on the bench to test it under (typically computer-) controlled conditions, measure its output, simulate different driving conditions, etc.
I've never heard any term except dyno (or dynamometer), but I much prefer those terms simply because it's more apparent to someone that doesn't have an understanding of engine & car testing.
I'm a fan of names that give insight into what the thing/product/service/company actually does.
dynos can measure at the engine (in which case they measure brake horse power) or at the wheels. Most individuals are more familiar with the ones that measure at the wheels, as that's how they would measure the effect of after-market modifications.