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."
in which the h-sound is produced in the back of the throat and the 'a' is silent, is the sound one makes to emphasize how empty an action, reaction or situation is.
"When I ejaculate it feels like nothing comes out... Phhha..."
Person 1: "You are 5 minutes late."
Person 2: "Phhha..."