rein in vs rein

rein in is not a noun while rein is a noun.

Word	Noun	Adjective	Verb	Adverb
rein in	No	No	Yes	No
rein	Yes	No	Yes	No

As verbs, rein in and rein are synonyms defined as:

rein in and rein: stop or slow up one's horse or oneself by or as if by pulling the reins

As verbs, rein in and rein are synonyms defined as:

As verbs, rein in and rein are synonyms defined as:

Other synonyms of rein in include draw rein, harness.

rein in (noun)	rein (noun)
	one of a pair of long straps (usually connected to the bit or the headpiece) used to control a horse
	any means of control

rein in (verb)	rein (verb)
stop or slow up one's horse or oneself by or as if by pulling the reins	keep in check
stop or check by or as if by a pull at the reins	stop or slow up one's horse or oneself by or as if by pulling the reins
control and direct with or as if by reins	stop or check by or as if by a pull at the reins
	control and direct with or as if by reins