Definition of flop:
(v) :
to fall heavily, because lacking energy; to
fail completely, not to be
successful at all (about a movie, play, book, song, etc.)
"he flopped down in front of the television as he was exhausted from work."
(n) :
an incident of a certain type of fall; a
plopping down; a
failure, especially in the entertainment industry
"look at the flop of hippies!"