WordNet (r) 3.0 (2006):

nose dive
    n 1: a steep nose-down descent by an aircraft [syn: dive,
         nose dive, nosedive]

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "nose dive":
   acrobatics, aerobatics, banking, beat down, belly buster,
   belly flop, belly whopper, break, breakdown, cannonball, chandelle,
   cheapen, cheapening, collapse, comedown, crabbing, crash,
   crash dive, cropper, cut, cut prices, decline, deflate, deflation,
   depreciate, depreciation, devaluate, devaluation, dip, dive,
   diving, downfall, drop, fall, fall in price, fishtailing, gainer,
   give way, glide, header, jackknife, jew down, lose altitude, lower,
   lowering, mark down, markdown, parachute, parachute jump, pare,
   pitch, plop, plummet, plummeting, plump, plunge, plunk, pounce,
   pounce on, pounce upon, power dive, pratfall, price cut,
   price fall, price reduction, pull-up, pullout, pushdown, reduce,
   reduction, rolling, running dive, sag, settle, shave, sideslip,
   skid, skin-dive, sky dive, sky-dive, slash, slump, smash, sound,
   spiral, stall, stationary dive, stoop, stumble, stunting,
   swan dive, swoop, swoop down, tactical maneuvers, tailspin,
   take a header, trim, tumble, volplane, zoom