An exlamation of disbelief
Joe-"I won the lottery!!"
Me-"Pft! Yeah right."
A sound made when you could really care less about the subject mentioned but don't want to verbally express how you feel.
Pft.
Pretty F***ing Terrible; the opposite of mmph (makes me pretty happy)
You listen to Kid Rock? PFT, no wonder you don't have a girlfriend.
the noise my dog makes when he farts
suddenly i heard my dog's rump go 'pffffftt'