WordNet (r) 3.0 (2006):

back out
    v 1: move out of a space backwards; "He backed out of the
         driveway"
    2: make a retreat from an earlier commitment or activity; "We'll
       have to crawfish out from meeting with him"; "He backed out
       of his earlier promise"; "The aggressive investment company
       pulled in its horns" [syn: retreat, pull back, back
       out, back away, crawfish, crawfish out, pull in one's
       horns, withdraw]