subclass

An object class derived from another class (its superclass) from which it inherits a base set of properties and methods.

A rank directly below class

A secondary class within a main class.

(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."

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