Definition of "caustic"

"How now!" said Scrooge, caustic and cold as ever.

1843, Charles Dickens, A Christmas Carol

The bargain was not concluded as easily as might have been expected though, for Scadder was caustic and ill-humoured, and cast much unnecessary opposition in the way

1843, Charles Dickens, Martin Chuzzlewit

Madame Beck esteemed me learned and blue; Miss Fanshawe, caustic, ironic, and cynical

1853, Charlotte Brontë, Villette

The Secretary and the Assistant-Secretaries would say little caustic things about him to the senior clerks, and seemed somewhat to begrudge him his new honours.

1857, Anthony Trollope, The Three Clerks

this set of worthies, who were only too prone to shut up their emotions with caustic words.

1886, Thomas Hardy, The Mayor of Casterbridge

The humor of my proposition appealed more strongly to Miss Trevor than I had looked for, and from that time forward she became her old self again; […] . Our table in the dining-room became again the abode of scintillating wit and caustic repartee, Farrar bracing up to his old standard, and the demand for seats in the vicinity rose to an animated competition.

1897 December (indicated as 1898), Winston Churchill, chapter VIII, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.

though he came too late / To join the martyrs, there was still a place / Among the tempters for a caustic tongue / / To test the resolution of the young / With tales of the small failings of the great

c. 1930, W.H.Auden, The Quest