unburn

un- +‎ burn

unburn (third-person singular simple present unburns, present participle unburning, simple past and past participle unburned)

1. (intransitive) To undergo the process of burning in reverse.
   • 2009, Bradley Harris Dowden, The Metaphysics of Time: A Dialogue, page 122:

     In your class last year we learned that increase in entropy is why matches burn but never unburn, why cans rust but never unrust, and why engines are never perfectly efficient.