hmmm... let me make some guesses...
1. cowboys are always associated wif ropes and lassos. Mebbe cowboy
sex means S&M?
2. cowboys are always riding. Hmmm... perhaps it means postions
where "riding" is involved?
3. cowboys buck a lot. and cowboys shoot a lot. Mebbe cowboy
ejaculations means bucking a lot when shooting?
4. cowboys, ironically are not particularly familiar wif cows. in
fact they should have been called horseboys. let me guess perhaps
the coyboy sex involves animals?
5. cowboys are well known to be bow-legged. perhaps it means that
pose during ejaculation?