BUT n.
The end; esp. the larger or thicker end, or the blunt, in distinction from the sharp, end. See 1st Butt. But end, the larger or thicker end; as, the but end of a log; the but end of a musket. See Butt, n.
CAUSTIC; CAUSTICAL a.
Severe; satirical; sharp; as, a caustic remark. Caustic curve (Optics), a curve to which the ray of light, reflected or refracted by another curve, are tangents, the reflecting or refracting curve and the luminous point being in one plane. -- Caustic lime. See under Lime. -- Caustic potash, Caustic soda (Chem.), the…