1
general::
1. Move or retreat backwards without turning; same as BACK AWAY, def. 1. 2. Also, back out of something. Withdraw from a situation, or break an agreement or engagement. For example, After the announcement appeared in the papers, Mary found it doubly difficult to back out of her engagement to Todd. [Early 1800s] Also see GO BACK ON.
American Heritage Idioms
2
general::
Phrase(s): back out (of something)
1. Lit. [for someone or something] to move out of something backwards. • The rabbit tried to back out of its burrow. • The rabbit backed out. 2. Fig. [for someone] to withdraw from something, such as an agreement, negotiations, an argument, etc. • Are you going to try to back out of our agreement? • You won’t back out, will you?, Phrase(s): back someone or something out (from something)
to back someone or something out of something. • Judy backed out the car from the parking place. • She backed it out from its space.
McGrawhill's American Idioms And Phrasal Verbs