An employee who works for an airline, that loads/ unloads luggage. Get's aircraft ready for the turn around (Next flight).
The ramp rats are getting the transatlantic flight ready for it's next trip.
Someone who hangs around the airport a lot. Generally, more ramp rats will be found in smaller, friendlier airports, where there are flight schools and such to mooch coffee off of.
The ramp is the large concrete area where planes are parked. Contrary to it's name, ramps are usually fairly flat.
See airport bum.
I made a good landing, even the ramp rats behind the fence thought so when they saw it.