A short sound created with the vibration of the lips; used for expressing disgust, sarcasm, attitude, or to just sound like a horse and annoy the hell out of people.
Person #1: "So, are you going to give me that money that you owe me?"
Person #2: "Phhbt! Yeah right."
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Random Person: "Hey everyone! Listen to what I can do! ... Phhbt!"
Everyone: "That's not hard to do you idiot, anyone can sound like a horse."
"Phbbbt" is the sound you make by putting your tongue between your lips and blowing. It is used when trying to show adverse feelings towards someone.
It is used mostly in instant messaging.
fun fact: in Yahoo! Messenger it has a dedicated emoticon: >:P , it's like :P but with a '>' in front of it, representing angry thoughts towards someone while sticking your tongue out
a: haha, my grade is higher than yours
a: you fail
b: >:P (phbbbt)
b: bite me
Making a fart noise. Used when you want to curse but your mommy and daddy does not allow you to. But you really want to and it does not matter what your mommy and daddy says. And you don't give a phbbbt.