THESAURUS
back out
abandon, abjure, back down, backpedal, backwater, beat a retreat, beg off, boggle, chicken, chicken out, climb down, crawfish out, cry off, deny, depart from, desert under fire, disavow, discard, disclaim, disengage, disown, draw back, draw off, drop out, eat crow, eat humble pie, evacuate, fall back, falter, forsake, forswear, funk, funk out, get cold feet, give ground, give place, go back, go back on, jettison, jilt, leave, leave behind, leave flat, lose courage, maroon, move back, pull back, pull out, quit, quit cold, recant, renege, renounce, repudiate, resile, retire, retract, retreat, revoke, run back, say goodbye to, scuttle, skedaddle, stand back, stand down, swallow, take back, take leave of, throw over, unsay, vacate, welsh, withdraw
ROGET THESAURUS
back out
Regression
VB
recede, regrade, return, revert, retreat, retire, retrograde, retrocede,
back out, back down, balk, crawfish, crawl, withdraw, rebound, go back, come back, turn back, hark back, draw back, fall back, get back, put back, run back, lose ground, fall astern, drop astern, backwater, put about, backtrack, take the back track, veer round, double, wheel, countermarch, ebb, regurgitate, jib, shrink, shy, turn tail, turn round, turn upon one's heel, turn one's back upon, retrace one's steps, dance the back step, sound a retreat, beat a retreat, go home.