Eine Strömung der Architektur, der Künste und der Philosophie, die auf die Moderne reagiert und in unterschiedlicher Weise charakterisiert wird, häufig besonders durch ihre Kritik am Universalismus der Moderne und die Betonung von Pluralismus, Eklektizismus und Werterelativismus.

1914
The raison d’etre of Post-Modernism is to escape from the double-mindedness of Modernism by being thorough in its criticism—by extending it to religion as well as theology, to Catholic feeling as well as to Catholic tradition.
J. M. Thompson: Post-modernism, in: Hibbert Journal 1914, S. 744.

1926
The Spirit of the Living God will create Postmodernism.
Bernard Iddings Bell: Postmodernism and Other Essays, Bd. 1, Milwaukee 1926, S. 54.

1977
The phrase ‘post-modern’ is not the most happy expression one can use concerning recent architecture. It is evasive, fashionable and worst of all negative – like defining women as ‘non men’. It doesn’t say immediately, like a good slogan, what banner to follow […] it is precisely this vagueness and implied pluralism which the title of this book is meant to convey. The present situation tolerates opposite approaches, and I hope that architecture doesn’t prematurely crystallise around a single style and doctrinaire approach, as it has so many times in this century. If there is a single direction I prefer, the reader will discover that it is pluralistic: the idea that an architect must master several styles and codes of communication and vary these to suit the particular culture for which he is designing. I have called this ‘adhocism’ in the past, and I use the term ‘radical eclecticism’ here to give this approach a name
Charles A. Jencks: The Language of Post-Modern Architecture, London 1977, S. 7.

1979
Simplifying to the extreme, I define postmodern as incredulity toward metanarratives. This incredulity is undoubtedly a product of progress in the sciences: but that progress in turn presupposes it. To the obsolescence of the metanarrative apparatus of legitimation corresponds, most notably, the crisis of metaphysical philosophy and of the university institution which in the past relied on it. The narrative function is losing its functors, its great hero, its great dangers, its great voyages, its great goal. It is being dispersed in clouds of narrative language elements—narrative, but also denotative, prescriptive, descriptive, and so on. Conveyed within each cloud are pragmatic valencies specific to its kind. Each of us lives at the intersection of many of these. However, we do not necessarily establish stable language combinations, and the properties of the ones we do establish are not necessarily communicable. […]
Obviously, a major shift in the notion of reason accompanies this new arrangement. The principle of a universal metalanguage is replaced by the principle of a plurality of formal and axiomatic systems capable of arguing the truth of denotative statements; these systems are described by a metalanguage that is universal but not consistent. What used to pass as paradox, and even paralogism, in the knowledge of classical and modern science can, in certain of these systems, acquire a new force of conviction and win the acceptance of the community of experts.
Jean François Lyotard: La condition postmoderne. Rapport sur le savoir, engl. Übers. The Postmodern Condition. A Report on Knowledge, Minneapolis 1994, S. xxiv; 43f.

2002
In this opposition of modern and postmodern, different architectural forms  were presented as expressive of contrasting social values, with the modern style symbolizing bureaucratic rationality, cold efficiency, uniformity and elitism and the postmodern style expressing playfulness, consumption and leisure orientation, variety, pluralism and egalitarianism.
Nico A. Wilterdink: The sociogenesis of postmodernism, in: European Journal of Sociology 43 (2002), S. 190-216, hier S. 196.