From my limited knowledge, a klunker is a balloon bike that has been owner modified for mountain biking. If I remember correctly, klunkers were around before commercially available mtb's.
Space bikes are space race inspired middleweight bikes of the early 60's. The most popular of these was the Sears Spaceliner. A lowrider is usually a 20" musclebike/ Stingray style framed bike, with a banana seat as low as possible, bent Springer forks to lower the front, and forward adjusted apehanger bars, and lots of chrome with whitewall tires.
A burrito bike is a long, low, stretched frame, usually owner built, with cranks moved forward of the seat, and the seat is usually in front of and lower than the top of the rear tire. A chopper is styled after a chopper motorcycle-a long front fork and a semi reclined seating position.