reinless

CIDE DICTIONARY

reinless, a. 

 Not having, or not governed by, reins; hence, not checked or restrained.  [1913 Webster]

ROGET THESAURUS

reinless

Laxity

N laxity, laxness, looseness, slackness, toleration, freedom, anarchy, interregnum, relaxation, loosening, remission, dead letter, brutum fulmen, misrule, license, licentiousness, insubordination, lynch law, nihilism, reign of violence, dethronement, deposition, usurpation, abdication, lax, loose, slack, remiss, weak, relaxed, licensed, reinless, unbridled, anarchical, unauthorized, adespotic.