Can be shorted to 'gas out'.
Or to reject an idea/suggestion.
Person A: "hey man, ready to go?, it's gonna be awesome!"
Person B: "...errrrm... actually i think i'm gonna gas it out.
Person A: "You're an idiot."
"I was going to see my bird last night but i thought i'd gas out and have a pot noodle and a wank instead"