implicature.org

Suppose that A and B are talking about a mutual friend, C, who is now working in a bank. A asks B how C is getting on in his job, and B replies, Oh quite well, I think; he likes his colleagues, and he hasn't been to prison yet. At this point, A might well inquire what B was implying, what he was suggesting, or even what he meant by saying that C had not yet been to prison. The answer might be any one of such things as that C is the sort of person likely to yield to the temptation provided by his occupation, that C's colleagues are really very unpleasant and treacherous people, and so forth. It might, of course, be quite unnecessary for A to make such an inquiry of B, the answer to it being, in the context, clear in advance. It is clear that whatever B implied, suggested, meant in this example, is distinct from what B said, which was simply that C had not been to prison yet. I wish to introduce, as terms of art, the verb implicate and the related nouns implicature (cf. implying) and implicatum (cf. what is implied). The point of this maneuver is to avoid having, on each occasion, to choose between this or that member of the family of verbs for which implicate is to do general duty.
—H. P. Grice, Logic and Conversation, 1975 (Based on lectures from 1967)

Note that the noun implicatum never caught on – even Grice didn't use it systematically – and that the noun implicature does double-duty both for the phenomenon of implicating and for a proposition that is implicated.