Refers to the terrible food combination of salsa with waffles, usually by people with psychopathic tendencies. Used metaphorically to describe something which is in incredibly poor taste or nonsensical.
"This car is spec'd horribly, the colors are horrendous. Whoever chose this must like salsa waffles."
Fucking someone in the ass while they pour spicy salsa down your urethra
Salsa is referring to the salsa down the urethra and Shake to the butt fucking
Jeffrey : You wanna set up a Salsa & Shake someday?
Frank : sure, but who's getting the salsa and who's getting shooken?
Jeffrey : I'll take salsa!
Frank : sure! But we need to find some good spicy Salsa!