subclass

noun

1. A secondary class within a main class.

   “1959, "Steam's Finest Hour" edited by David P. Morgan, Kalmbach Publishing Co., referring to the R-1 Mountain class loco. These 4-8-2's, of which B&M eventually purchased 18 in various subclasses, could almost haul the tonnage of a T and more than made up for the slight deficiency by raising the maximum speed limit from 45 to 70 miles per hour, thanks to 73-inch drivers.”

   “Goffin is a prose text interspersed with short lists of typical terms exemplifying certain sub-classes of Indian English lexis.”

2. A rank directly below class.
3. An object class derived from another class (its superclass) from which it inherits a base set of properties and methods.

verb

1. (transitive)(in object-oriented programming) To create a subclass of (some class).

   “I subclassed the Button class to create a more specialised FancyButton class for my user interface.”

2. (transitive)To cause (an object) to act as an instance of a subclass (by creating the desired subclass and instantiating an object of this subclass).

   “Since Windows knows about these events, your application should be able to know about them as well. In order to accomplish this, subclass the window of a form or control, intercepting all of its events.”