Not wearing or being fitted with a bridle: an unbridled pony. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "unbridled" in a sentence
"All week, Glenn Beck has been railing against what he called the unbridled consumption of America."
"On nuclear weapons, the Iranian president deplores what he calls unbridled expansion and testing of more powerful warheads, apparently implicating the United States."
"Waldo there has been a lot of development but "unbridled" is not exactly, uhhh …. correct."