i-adjective
sharp-tongued; cutting; scathing
Describes speech, criticism, or a person's way of speaking that is incisive, harsh, or piercing. Often used in formal or written contexts.
彼の舌鋒鋭い批判に、誰も反論できなかった。
No one could argue against his scathing criticism.
舌鋒鋭い質問が相次いだ。
Sharp questions came one after another.
辛辣 is a na-adjective meaning 'bitter' or 'severe' in criticism. 舌鋒鋭い is more literary and emphasizes the cutting, eloquent nature of the words.
Compound of 舌鋒 (ぜっぽう, 'tip of the tongue; eloquence') and 鋭い (するどい, 'sharp'). The exact historical derivation is uncertain, but the combination is a natural metaphorical extension.