Searle does not precisely define the former as such, but rather introduces several possible illocutionary forces by example.

An utterance is said to have illocutionary force and perlocutionary force.

What is the illocutionary force of the sergeant's last utterance in Task 19?

How does A exploit ambiguity in the illocutionary force of what is said?

One example occurs when the terms locution and illocutionary force are first used (p.12).

That explains why illocutionary force can be deployed without exerting muscular effort.

Users may also use spellings that reflect their illocutionary force and intention rather than using the standard spelling.

But they can have other illocutionary forces or additional modal components:

Step 5: If steps 1-4 do not yield a consequential meaning, then infer that there are two illocutionary forces at work.

Several speech act theorists, including Austin himself, make use of the notion of an illocutionary force.