Strong's #7448: recen (pronounced reh'-sen)
 from an unused root meaning to curb; a halter (as restraining); by implication, the jaw:--bridle.
Brown-Driver-Briggs Hebrew Lexicon:
 
  resen 
 
 1) something that restrains, halter, jaw
 
 1a) halter
 
 1a1) of restraint thrown off (figuratively)
 
 1b) jaw (of crocodile)
 
  Part of Speech: noun masculine
Relation: from an unused root meaning to curb
Usage:
This word is used 4 times:
Job 30:11: "my cord, and afflicted me, they have also let loose  the bridle before"
Job 41:13: "or who can come to him with his double  bridle?"
Psalms 32:9: "whose mouth must be held in with bit  and bridle, lest they come near unto thee."
Isaiah 30:28: "the nations with the sieve of vanity:  and there shall be a bridle in the jaws of the people, causing them to err."