In the "Tremors" trilogy, the monsters start out as giant underground worms called "graboids", then develop into walking two-legged beasts called "shriekers", and finally into rocket-propelled flying predators called... well, if I'd been a character in the story, I would've dubbed them "rocket dragons". But instead the folks in the movie name them "ass-blasters". Tuh!
I'm not really bothered by all that; it just seems a tad unimaginative. :}