All 4 Uses

caustic
in
The Devil in the White City
(Edited)

From the start there was tension between the two firms, although no one could have known it would erupt years later in a caustic attack by Sullivan on Burnham's greatest achievements, this after Sullivan's own career had dissolved in a mist of alcohol and regret.
p. 30.2

caustic = harsh
The civility of this encounter belied a caustic battle being waged outside Jackson Park for the rights to illuminate the exposition.
p. 131.4
Some days the halls were suffused with a caustic scent, as of a cleanser applied too liberally, other days with a silvery medicinal odor, as if a dentist were at work somewhere in the building easing a customer into a deep sleep.
p. 256.4 *
The next day the newspaper singled out Chauncey Depew, president of the New York Central, for a particularly caustic appraisal.
p. 310.9 *

caustic = critical or harsh

Definitions:

(1) (caustic as in: a caustic chemical)
damaging or harsh -- often of a corrosive chemical like a strong acid
(2) (caustic as in: a caustic person)
sarcastic, critical, or harsh
(3) (meaning too rare to warrant focus)