adj

• (archaic) Harsh and sharp, or bitter and not pleasant to the taste; acrid, pungent.
  "The old man […] began to suffer in the body as well as the mind. He had formed the determination of setting out in person for Dumfriesshire, when, after having been dogged, peevish, and snappish to his clerks and domestics, to an unusual and almost intolerable degree, the acrimonious humours settled in a hissing-hot fit of the gout, which is a well-known tamer of the most froward spirits, […]"
• (figuratively) Angry, acid, and sharp in delivering argumentative replies: bitter, mean-spirited, sharp in language or tone.
  "Theſe points are diſcuſſed with the ability and learning which diſtinguiſh the Right Reverend Author's [Samuel Horsley's] publications, but not without acrimonious expreſſions of contempt and indignation againſt his opponent [Joseph Priestley]."