In J. L. Austin’s theory a “speech act” is an utterance that achieves some action by virtue of its being spoken, “I thee wed,” “I hereby open the 23rd International …”, etc. but not “The king of France is bald,” “Did you go to the party yesterday?”, etc.
I have recently witnessed an inclination at workshops in religious studies to refer to magic as speech acts. The motivation is to not dismiss magic as hocus pocus, but instead take an emic perspective; the effort fails. To claim that hoc est corpus … constitutes a speech act is to admit that nothing essential happens to the bread and thereby rejects the emic. The more respectful participant observer would admit the magic is magic and admit it works.
Linguists have stretched “speech acts” yet further; to them it is simply a synonym for ”utterance”. Speaker and hearer are dubbed “speech act participants”, which, in the perennial quest to make prose opaque, become SAPs. This choice of terminology is particularly unfortunate because in Austin’s formulation a third person, such as the witness at a wedding, is often a participant in a speech act. If somehow Linguists cannot bear the tired old words “speaker” and “hearer” they could try ”interlocutors”, but please let Austin have speech acts, without attempting to bathe in his reflected glory.