S. Schiffer: 'Meaning' (1972)

Stephen Schiffer defines the term 'Illocutionary Act' within his book 'Meaning' (1972), which is chiefly concerned with the question of how to analyse adequately the notion of 'speaker meaning' (as famously targetted by Grice). He defines "Illocutionary Acts" as acts 'of speaker meaning' (cf. ibid., 91-2, 103), of which, in turn, he assumes two basic types. Here is his definition in full.  

The class of kinds of illocutionary acts divides into two jointly exhaustive and mutually exclusive subclasses. Let us designate one class the "˫" class of kinds of illocutionary acts [read: 'the assertive class …'],  and the other the "!" class of kinds of illocutionary acts [read: 'the imperative class …'].

A kind of illocutionary act I is an ˫ kind of illocutionary act if and only if, for any S and any x, S performed an act of kind I in uttering x only if, for some p, S meant that p by uttering x. Telling that, objecting, reporting, predicting, and replying are examples of ˫ kinds of illocutionary acts.

A kind of illocutionary act I is an ! kind of illocutionary act if and only if, for any S and any x, S performed an act of kind I in uttering x only if, for some A and some ψ, S meant that A was to ψ by uttering x. Ordering, requesting, entreating, and asking are examples of ! kinds of illocutionary acts. (Schiffer 1972, 95)

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Schiffer, S. (1972), Meaning, Oxford: Oxford University Press.