D'eculassement \D['e]`cu`lasse`ment"\, n. [F.] Also, sometimes, Anglicized Deculassment \Dec`u*lass"ment\(Ordnance) An accidental blowing off of, or other serious damage to, the breechblock of a gun; also, a removal of the breechblock for the purpose of disabling the gun. [Webster 1913 Suppl.]