In object oriented programming a method which performs some operation in a class, as opposed to performing it on a particular instance (like instance methods do). They are also called static methods in C++ and Java.
One special type of class method is the constructor, because it's called upon the class, and can't be inherited. What makes a constructor a special kind of constructor in Java and C++ is that its scope is "adjusted" to that of the instance being created. But don' t take my word for this, few people believe me when I tell them this.. =).