back out vs pull back

back out and pull back both are verbs.

Word	Noun	Adjective	Verb	Adverb
back out	No	No	Yes	No
pull back	No	No	Yes	No

As verbs, back out and pull back are synonyms defined as:

back out and pull back: make a retreat from an earlier commitment or activity

Other synonyms of back out include back away, crawfish, crawfish out, pull in one's horns, retreat, withdraw.

back out (verb)	pull back (verb)
make a retreat from an earlier commitment or activity	make a retreat from an earlier commitment or activity
move out of a space backwards	move to a rearward position; pull towards the back
	stretch back a bowstring (on an archer's bow)
	use a surgical instrument to hold open (the edges of a wound or an organ)
	pull back or move away or backward