Upside Down
noun, な adjective, の adjective
Something is reverse, that much you know. The さま comes from 様, which could mean manner. So, something that is in a "reverse manner," is something that is upside down.
The reading comes from 逆らう and 様, put together. A bit of an upside down reading if I do say so myself, but you do what you gotta do.
どうして蝶々を逆さまに描いたの？
Why did you draw the butterfly upside down?