subclass

Short definition from Wiktionary

Noun

1. 1
   A secondary class within a main class.
2. 2
   A rank directly below class.
3. 3
   An object class derived from another class (its superclass) from which it inherits a base set of properties and methods.

Verb

1. 1
   (in object-oriented programming) To create a subclass of (some class).
2. 2
   To cause (an object) to act as an instance of a subclass (by creating the desired subclass and instantiating an object of this subclass).