WordNet (r) 3.0 (2006):

let go
    v 1: release, as from one's grip; "Let go of the door handle,
         please!"; "relinquish your grip on the rope--you won't
         fall" [syn: let go of, let go, release, relinquish]
         [ant: hold, take hold]
    2: be relaxed; "Don't be so worried all the time--just let go!"

Moby Thesaurus II by Grady Ward, 1.0:

217 Moby Thesaurus words for "let go":
   abandon, abjure, absolve, acquit, amnesty, be caught napping,
   be neglectful, be negligent, boot, bounce, break, break up, bump,
   bust, can, carouse, cashier, cast loose, celebrate, clear,
   come off, cut, cut loose, cut out, deactivate, debauch, debrief,
   decontaminate, default, defrock, degrade, demob, demobilize,
   demote, deplume, depose, deprive, desist, destigmatize, detach,
   diffuse, disband, disbar, discharge, discontinue, disemploy,
   disintegrate, disjoin, dismiss, disorganize, dispense from,
   dispense with, disperse, displace, displume, disregard, dissolve,
   disuse, drop, drum out, ease, ease off, except, exculpate, excuse,
   exempt, exempt from, exonerate, expel, fail, fire, forgive, free,
   furlough, give absolution, give dispensation from, give over,
   give the ax, give the gate, give up, give way to, gloss over,
   go all out, go bail for, go flat out, go separate ways,
   go unrestrained, goldbrick, goof off, grant amnesty to,
   grant bail to, grant immunity, grant remission, have done with,
   hell around, ignore, jollify, jolly, jump, justify, kick,
   kick upstairs, lapse, lark, lay off, leave, leave go,
   leave loose ends, leave off, leave undone, let alone, let be,
   let dangle, let go, let go free, let loose, let loose of, let off,
   let off steam, let out, let pass, let ride, let slide, let slip,
   let up, loose, loosen, lose sight of, lose track of, make merry,
   make redundant, make whoopee, malinger, miss, muster out, neglect,
   nod, nol-pros, nonpros, not care for, not get involved, not heed,
   not pursue with, not think, omit, open up, overlook, pardon,
   parole, part, part company, pass over, pass up, pension off,
   pretermit, procrastinate, purge, put behind one, put on parole,
   quash the charge, quit, raise hell, read out of, relax, release,
   relinquish, remise, remit, remove, renounce, replace, resign,
   retire, revel, roister, run wild, sack, save the necessity,
   scatter, see life, separate, separate forcibly, set free, shirk,
   shrive, skip, skylark, slack, slack off, slacken, sleep, spare,
   split up, spree, step out, stop, strip, superannuate, surplus,
   suspend, take for granted, trifle, turn off, turn out, unclasp,
   unclutch, unfrock, unglue, unhand, unleash, unstick, vindicate,
   waive, wanton, whitewash, whoop it up, withdraw the charge