(computing, programming, transitive) To cause (a previously subclassed window or object) no longer to act like a member of a subclass.
1990, Paul W. Cheatham, ‎David E. Reich, ‎Robert F. G. Robinson, OS/2 presentation manager programming (page 339)A good convention for working with multiple subclasses is to only subclass the window procedure that is the first in the call chain and only unsubclass the one that is first.
1996, Ted Coombs, ‎Jason Coombs, ‎Don Brewer, The Netscape LiveWire SourcebookUnsubclassing the plug-in window ensures that Navigator can continue to function normally once the plug-in module is unloaded.
1997, Douglas A. Young, Netscape developer's guide to plug-ins (page 177)It is very important to remember to unsubclass the plug-in window when the plug-in is destroyed.
