Are you a real person?
Guac is just short for guacamole. What are you, insane? Haven't you been to Chipotle? Holy crap. Honestly, send me an email (danny at heavy dot com) and explain why you clicked on this.
What?! You don't know what guacamole is?! Ok, wow. It's a Mexican dip that has avocados, tomatoes, and onions in it and the avocados are all smooshy and look-- it's the best dip in the world, besides maybe hummus. You serve it cold and it's just freaking phenomenal.
Why do people say guac?
People say guac because they're lazy and "guacamole" has 14 syllables and ain't no one got time for that.