1) to seriously fuck up a situation
2) to suck a given dick
3) to expel air out of the mouth toward an object
1) Liz really blew it when she started using her teeth while blowing it.
2) "Well, I'm on my knees. What should I do now?"
3) "I actually meant SUCK it, ya dumb bitch (SMACK!)"
To mess up, but not in a big way.
Don't blow it, man! You're so stupid, I know you're going to blow it!