This rare adjective describes something or someone that cannot be held back, checked, or restrained. The term combines the negative prefix with the verb 'to hold' or 'to restrain,' creating a vivid picture of irresistible force or uncontrollable impulse. In classical usage it could describe both impersonal forces (like an unstoppable rush or impulse) and personal characteristics (an uncontrollable person). The word carries connotations of something wild, untamed, or beyond the reach of restraint—whether that's a force of nature or human passion that breaks through every barrier.