The ability of the mind to
refer to something, the quality of a
thought to be about something, to have
meaning.
This is the crucial notion in John Searle's discussion of the question "Can machines think?" He argues machines will never think because they lack intentionality, and presents his Chinese room thought experiment to support that position.
It goes without saying that language carries meaning, and that without intelligence (understanding) on the part of the receiver, successful communication is impossible. But this doesn't mean that we have to take a quality of 'intentionality' for granted, and presuppose it as a way to distinguish sentient beings from non-sentient beings.
This is what Searle does in his well-known Chinese room argument.