According to my 30th Anniversary Edition Collins English Dictionary, (of which I am generally very fond) a locutionary act is the act of uttering a sentence considered only as such.
And if that means anything at all to you then you're a lot cleverer than I am.
Word To Consider Today: locutionary. This word comes from the Latin locūtiō, an utterance.
I've done some research, and the basic idea here seems to be that a locutionary act is to do with the actual meaning of the words you're saying. It's not an implied meaning (if you say I'm mad about Harry then you're probably not claiming to be mentally ill) and it's not anything that happens as a by-product of the words (for example, if someone shouts watch out! then you've been told to move, even though no one has uttered the word move).
The idea of analysing utterances in this way was dreamt up by JL Austin (though probably not when he was actually asleep).