Pantsload means any of the following:
A) A euphemism
Gee, mom, that's a pantsload of ducks over there!
B) A load of something
sufficient to fill a pair of trousers
After having sex on the beach, Andrea and her partner Rick both found themselves with pantsloads of sand.
C) Loosely, an unreasonably large
amount of something.
20 terabytes? That's a pantsload of disk space!