(aviation, travel) (in a reservation system) The letter used to signify a particular fare level.

(regular expressions) Characters which are excluded in a pattern.

(US, colloquial) An introductory university course that is designed to "weed out" those students who are not able to pass it.

(sociology) A participant in class warfare.

(martial arts) A division of competition used to match competitors against others of their own weight

(linguistics) A linguistic form class whose members are words.

Of the highest quality.

plural of school class

plural of pitch class

(object-oriented programming) A class from which other classes can be derived, inheriting its functionality or interface; a potential superclass for subclasses.