Definition of "sententiously"

"We shall see to-morrow," said the doctor. "We shall," replied Lady Anne, very sententiously.

1842, [anonymous collaborator of Letitia Elizabeth Landon], chapter LXI, in Lady Anne Granard; or, Keeping up Appearances. […], volume III, London: Henry Colburn, […], page 155

He became very cool and collected all at once. ‘I am not such a fool as I look, quoth Plato to his disciples,’ he said sententiously, emptied his glass with great resolution, and we rose.

1899 February, Joseph Conrad, “The Heart of Darkness”, in Blackwood’s Edinburgh Magazine, volume CLXV, number M, New York, N.Y.: The Leonard Scott Publishing Company, […], part I, page 201