A exclaimation, mostly used in written form. Used to convey a feeling of excitement, satisfaction or joy. Has been described as the new w00t
, however is not as popular.
Derived from J. K. Rowling's fictional creature, the Fwooper, which sings an (at first) enjoyable song which eventually drives the listener insane.
Repetitive use of the word "Fwoop" has the potenial to do the same thing.