1) A sexual position wherein one partner lays on his/her back, with his/her head on the edge of a bed (or similar) and performs fellatio on a male partner that is standing in such a manner as to thrust his penis forcefully into his partner's open mouth.
2) An small alcoholic beverage meant to be consumed in one gulp or "shot," consisting of equal parts tequila and Goldshlagger.
1) "Tracy let me do a 'Mexican brain surgeon' last night!"
2) "Things went quickly downhill after that last round of 'Mexican brain surgeons.'"
Bonus combination example: "I met Jenna at the bar when we both ordered a 'Mexican brain surgeon." We toasted together and joked around a bit, then ordered another round. Fortunately, the liquid 'Mexican brain surgeon' did its job and I was able to do my own 'Mexican brain surgeon' on Jenna later that night. Giggitty.