Definition of "nonsensical"

Well, her very foolish grandmother has mixed herself up in some nonsensical correspondence with the court of St. Germains; or, rather, has let herself be made a tool by Mr. Trevanion, who, I am happy to say, is not Ethel's husband; they arrested him just in time.

1837, L[etitia] E[lizabeth] L[andon], “Prudence in Politics”, in Ethel Churchill: Or, The Two Brides. […], volume II, London: Henry Colburn, […], page 179