Down here a Pick-up is the person of the other gender you met in the pub last night for a fun time, while in the US it's a truck. Personally, I think our pick-ups are more fun.
Believe me, we have the same definition for "pick-up", but like most English words, it has multiple definitions. Only, our "pick-up" includes more than just "opposite sex" couplings, as the gays use it quite a bit too.
By the way, if I'm not mistaken, "Pickup" (for a flatbed truck) is more a marketing term invented purely to sell the product rather than a 'natural use' English word.