Wiktionary
n. (context philosophy English) A metatheoretical stance that critiques and amends positivism. While positivists believe that the researcher and the researched person are independent of each other, postpositivists accept that theories, background, knowledge and values of the researcher can influence what is observed. They believe that human knowledge is based not on unchallengeable, rock-solid foundations, but rather upon human conjectures.
Wikipedia
In philosophy and models of scientific inquiry, postpositivism (also called postempiricism) is a metatheoretical stance that critiques and amends positivism. While positivists believe that the researcher and the researched person are independent of each other, postpositivists accept that theories, background, knowledge and values of the researcher can influence what is observed. However, like positivists, postpositivists pursue objectivity by recognizing the possible effects of biases.
In international relations theory, postpositivism refers to theories of international relations which epistemologically reject positivism, the idea that the empiricist observation of the natural sciences can be applied to the social sciences.
Postpositivist (or reflectivist) theories of IR attempt to integrate a larger variety of security concerns. Supporters argue that if IR is the study of foreign affairs and relations, it ought to include non-state actors as well as the state. Instead of studying solely high politics of the state, IR ought to study world politics of the everyday world—which involves both high and low politics. Thus, issues such as gender (often in terms of feminism which generally holds salient the subordination of women to men—though newer feminisms allow for the reverse too) and ethnicity (such as stateless actors like the Kashmiris or Palestinians) can be problematized and made into an international security issue—supplanting (not replacing) the traditional IR concerns of diplomacy and outright war.
The postpositivist approach can be described as incredulity towards metanarratives—in IR, this would involve rejecting all-encompassing stories that claim to explain the international system. It argues that neither realism nor liberalism could be the full story. A postpositivist approach to IR does not claim to provide universal answers but seeks to ask questions instead. A key difference is that while positivist theories such as realism and liberalism highlight how power is exercised, postpositivist theories focus on how power is experienced resulting in a focus on both different subject matters and agents.
Often, postpositivist theories explicitly promote a normative approach to IR, by considering ethics. This is something which has often been ignored under traditional IR as positivist theories make a distinction between positive facts and normative judgements—whereas postpostivists argue that discourse is constitutive of reality; in other words, that it is impossible to be truly independent and factual as power-free knowledge cannot exist.
Postpositivist theories do not attempt to be scientific or a social science. Instead, they attempt in-depth analysis of cases in order to "understand" international political phenomena by asking relevant questions to determine in what ways the status-quo promote certain power relations. However, since they do not apply any scientific methods in researching or answering these questions - and instead employ rhetoric and obscurantism - postpositivists are not taken seriously by most academics.