2; a person who commits a random or insane act of stupidity which leaves some in disbelief.
3; a Bitch.
2; "Did you see that? he just ran across the highway. What a Barlow."
3; "Andrew is cool sometimes, but mostly he's just a Barlow."
If Barlow is your last name, it tends to be a good substitute for a first name if yours is as bland as mine (or you just happen to go by your last name).
2. Hey Barlow, what's up?
barlow- "*head swells* ffffffffffffffffffffffffffffffffffrrrrrfffff