Full Idea
For a statement to have (non-naturally) meant something, not merely must it have been 'uttered' with the intention of inducing a certain belief, but also the utterer must have intended an 'audience' to recognise the intention behind the utterance.
Clarification
He gives 'spots mean measles' as a 'natural' meaning
Gist of Idea
Meaning needs an intention to induce a belief, and a recognition that this is the speaker's intention
Source
H. Paul Grice (Meaning [1957], p.43)
Book Reference
'Philosophical Logic', ed/tr. Strawson,P.F. [OUP 1973], p.43
A Reaction
This is Grice's famous and distinctive theory of meaning. I am struck by the problem of a password, which seems to have a quite different intention from its literal meaning. Also a speaker with two different audiences and opposite intentions.