WordNet (r) 3.0 (2006):

bear down on
    v 1: sail towards another vessel, of a ship [syn: bear down
         on, bear down upon]
    2: exert a force with a heavy weight; "The snow bore down on the
       roof" [syn: drag down, bear down, bear down on, press
       down on, weigh down]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "bear down on":
   accost, advance, advance against, advance upon, approach,
   approach anchorage, appropinquate, approximate, bear against,
   bear down upon, bear hard upon, bear up, bear up for, bear up to,
   close, close in, close with, come, come closer, come forward,
   come near, come on, come up, confront, counterattack, draw near,
   draw nigh, drive, encounter, fetch, flank, gain upon, gas,
   go aboard, go alongside, high-pressure, infiltrate,
   launch an attack, lay aboard, lay for, lay in, lean on, lie in,
   make, make at, make for, march against, march upon,
   mount an attack, narrow the gap, near, open an offensive, press,
   pressure, proximate, push, put away for, put in, put into port,
   put pressure on, reach, run for, sail for, sidle up to, squeeze,
   stand for, steer toward, step up, strike, thrust