WordNet (r) 3.0 (2006):

open up
    v 1: cause to open or to become open; "Mary opened the car door"
         [syn: open, open up] [ant: close, shut]
    2: become available; "an opportunity opened up" [syn: open,
       open up]
    3: make available; "This opens up new possibilities" [syn:
       open, open up]
    4: open up an area or prepare a way; "She pioneered a graduate
       program for women students" [syn: pioneer, open up]
    5: start to operate or function or cause to start operating or
       functioning; "open a business" [syn: open, open up] [ant:
       close, close down, close up, fold, shut down]
    6: become open; "The door opened" [syn: open, open up] [ant:
       close, shut]
    7: talk freely and without inhibition [ant: be quiet, belt
       up, button up, clam up, close up, dummy up, keep
       mum, shut up]

Moby Thesaurus II by Grady Ward, 1.0:

188 Moby Thesaurus words for "open up":
   acknowledge, admit, admit everything, advance, aid, air, allow,
   appear, avow, bare, branch, branch out, breach, break the seal,
   bring before, bring forward, bring to light, bring up, broach,
   chink, clear the way, cleave, come clean, come forth,
   commend to attention, concede, confess, cop a plea, crack,
   crevasse, cut, cut loose, cut open, deploy, develop, disclose,
   discover, dismask, dispart, disperse, display, divaricate, divide,
   divulge, draw the veil, ease, expand, expedite, explain, expose,
   extend, facilitate, fan, fan out, fissure, flare, fly open,
   give out, give way to, go all out, go flat out, go unrestrained,
   grant, grease, grease the ways, grease the wheels, hasten,
   have no secrets, help along, impart, incise, introduce, launch,
   lay bare, lay before, lay open, let daylight in, let go, let loose,
   let on, let out, loose, lubricate, make a motion, make clear,
   make known, make public, make way for, manifest, materialize, moot,
   move, offer a resolution, oil, ope, open, open fire, open the way,
   out with it, outspread, outstretch, overgrow, overrun, own, own up,
   part, pave the way, plead guilty, pose, postulate, prefer,
   prepare the way, propose, proposition, propound, put forth,
   put forward, put it to, put out, quicken, raise the curtain,
   ramify, recommend, remove friction, rent, reveal, rift, rip, rive,
   run interference for, run wild, separate, set before, set forth,
   show, show up, simplify, slit, smooth, smooth the way,
   soap the ways, speak out, speak up, speed, spill, spill it,
   spit it out, splay, split, spraddle, sprangle, sprawl, spread,
   spread like wildfire, spread out, spring open, start, strip bare,
   submit, suggest, swing open, take a stand, tap, tear, tear open,
   tell all, tell the truth, throw open, unbar, unblock, uncloak,
   unclog, uncover, undrape, unfold, unfurl, unjam, unkennel, unmask,
   unpack, unroll, unscreen, unsheathe, unshroud, unveil, unwrap,
   ventilate, widen