thumb drives

Okay, I feel like an idiot, but I have a device that I bought because it was advertised as a thumb drive but which is not. It does not fit in the USB port and is slightly wider (the flat way) and flatter. I got a bunch of other ones at the same time which are regular-sized and work fine. What...

I thought they were called memory sticks, at least, but it seems every time someone hands one over at work, they're called something different... Flash drive? Thumb drive? And other things that didn't register on my radar. What's the coolest geek term for these doovelackies?