From Much Ado About Nothing, Act II, scene i, this is an example of clever wordplay by Benedick. Using an analogy, Benedick compares Beatrice to a dish of food, which he does not care for. He goes on to make a pun, using the epithet "Lady Tongue" not only to stand for Beatrice (as a metonym), but also the type of meat she is (tongue, a commonly eaten food in those days--not human, of course, but cow's). In other words, Benedick is saying that all Beatrice does is talk.
Benedick's joke would have gotten many laughs on stage in Shakespeare's day, for women were often stereotyped as being gossipers and loose-lipped. Ironically, it is Benedick who talks as much, or more, than Beatrice, so his words are used as verbal irony by Shakespeare to show the sexist double standard.
It is important to note that men judged women's talk as they did their promiscuity, meaning that the more a woman talked, the more she went to bed. So, there is a bit of innuendo in Benedick's statement as well.