A secondary coffee taste sensation characterized by a sour sensation on the back sides of the tongue. Caused by higher-than-normal percentage of sour acids and a high concentration of salts. This is relatively common in unwashed coffee from the Americas but is very rare in Ethiopian coffees.
harsh or corrosive in tone; "an acerbic tone piercing otherwise flowery prose"; "a barrage of acid comments"; "her acrid remarks make her many enemies"; "bitter words"; "blistering criticism"; "caustic jokes about political assassination, talk-show hosts and medical ethics"; "a sulfurous denunciation"
This is basically the opposite of a high acidity coffee and refers to the sour aftertaste that the coffee leaves in your mouth. Acrid flavors are generally seen as a flavor defect and are often the result of poor processing or low quality beans.