You you stick a burrito in your partners mouth, have sex with it, and then eat it afterwards.
I gave your sister a Mexican Burrito yesterday.
A mexican burrito is where a (wo)man shits out a log into a condom and freezes it. Then proceds to use the shitcicle as a dildo until thawed out.
Man: Erin is too kinky for me, bitch showed me her Mexican Burrito in action last night.
A Mexican Burrito is when you are having anal sex and the chick shits on your dick, making your dick all shitty. You then give her a shit stache, literally.. you give her a mustache with the shit on your dick.
Santiago: "ay senor i just gave anita a mexican burrito!"
Perijo: "oy good job comrade!"