Bucking-Kinda the same as curving someone, making someone else feel scared, or not wanting to do something G, or cool. Used in the south, watch out a lot of friends will say your bucking just because you don't want to do something they want!!!
basically, a guy rubs his hard cock on the groove on the back of a girl, right above her ass until he cums all over her back.
yeah man, me and julia were bucking last night. i jacked off my huge cock between that little groove in her back and came all over her back and her hott ass.
Rogering someone that the Bucker considers to be a complete and utter bastard, usually anally and with an inanimate - or animate if the occasion calls for it - object.
Man 1: I've just had a thought. Let's buckMatthew Caris with a jar of marmalade.
Man 2: Yes, his crack is big enough! Let's go!
*Men walk to the Marmalade Shop*