What is "performative utterance"

n. (context philosophy linguistics English) A sentence or other linguistic expression which, when expressed in an appropriate context, actually does or accomplishes something.

In the philosophy of language and speech acts theory, performative utterances are sentences which are not only describing a given reality, but also changing the social reality they are describing.

In his 1955 William James lecture series, which were later published under the title How to Do Things with Words, J. L. Austin argued against a positivist philosophical claim that the utterances always "describe" or "constate" something and are thus always true or false. After mentioning several examples of sentences which are not so used, and not truth-evaluable (among them non-sensical sentences, interrogatives, directives and "ethical" propositions), he introduces "performative" sentences or Illocutionary act as another instance.