abruptly bang blubber boil boil over bubble bubble over bubble up burble cast cave cave in chuck clap dash decline dive droop drop effervesce exactly fall ferment fizz fizzle fling flop flop down flump flump down flush founder full give way go down guggle gurgle hastily hiss hurl impetuously impulsively kerplunk lapse like a flash like a thunderbolt lower nose-dive of a sudden on short notice parachute pitch plank plop down plumb plummet plump plunge plunk point-blank pop pounce pounce on pounce upon precipitantly precipitately precipitously precisely right sag seethe set settle settle down sharp simmer sink sink down skin-dive sky-dive slap slouch slump slump down smack smack-dab sound spang sparkle square squarely startlingly stoop straight submerge subside sudden suddenly surprisingly swag swoop swoop down take a header throw thrust toss unawares unexpectedly without notice without warning work