arsenic trioxide

ar·se·nic trioxide

noun \ˌärs-nik-, -^ən-ik-\

Definition of ARSENIC TRIOXIDE

: a poisonous trioxide As₂O₃ or As₄O₆ of arsenic that was formerly used in medicine and dentistry but has been abandoned for therapeutic purposes and is now used especially as an insecticide and weed killer—called also arsenic, arsenious acid, arsenious oxide, white arsenic