unburn

present singular third person unburns · participle present unburning · participle past unburned · past unburned

1. intransitiveTo undergo the process of burning in reverse.

   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.

   2009, Bradley Harris Dowden, The Metaphysics of Time: A Dialogue, page 122

   1 more example

   Similarly, you cannot 'unstir' the sugar from a cup of coffee once it has been dissolved, and you never see a pile of ash in the fireplace 'unburn' to become a log of wood again.

   2002, Jim Al-Khalili, Black Holes, Wormholes and Time Machines, page 122