captmu2,
Service ceiling is altitude where 100fpm climb can be sustained. (50fpm for multi engine with one engine inop)
Absolute ceiling is altitude where airspeed for best angle of climb equals airspeed for best rate of climb (in effect, 0fpm, I guess!)
Not sure of the exact textbook definitions, but pretty close.
For turbine, I think absolute is defined as altitude where max available power is required to maintain level flight. Been a while, but I'll look it up and post here unless someone else does it first!