chlo·ro·acetophenone \| ̷ ̷ ̷ ̷+\noun orchlor·acetophenone\(|)klōr, -ȯr+\ (-s) Etymology:chlor- + acetophenone : a chlorine derivative of acetophenone; specifically: the alpha derivative C6H5COCH2Cl obtained as irritating white crystals by reaction of benzene and chloro-acetyl chloride or by chlorination of acetophenone and used especially in solution as a tear gas — called also phenacyl chloride