diacaustic

from The Century Dictionary.

• In mathematics, belonging to a species of caustic curves formed by refraction.
• noun [In math. sense, from the adj. diacaustic, above; in med. sense, of same formation, with reference to caustic in its literal sense.]
• noun In medicine, a double-convex lens, employed to cauterize apart.
• noun A diacaustic curve. See I.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Opt.) Pertaining to, or possessing the properties of, a species of caustic curves formed by refraction. See Caustic surface, under caustic.
• noun (Med.) That which burns by refraction, as a double convex lens, or the sun's rays concentrated by such a lens, sometimes used as a cautery.
• noun (Math.) A curved formed by the consecutive intersections of rays of light refracted through a lens.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Relating to the caustic curves formed by the refraction of light.
• noun A refracting lens, which can be used to cauterise.
• noun The curve or surface formed by the intersection of refracted light rays.