Wiktionary
n. (context organic compound English) The di-ethyl ester of phthalic acid; a clear liquid used as a solvent, insect repellent and in perfumes.
Wikipedia
Diethyl phthalate (DEP) is a phthalate ester, namely the diethyl ester of phthalic acid. It is a clear substance that is liquid at room temperature and is only slightly denser than liquid water. It has a faint, disagreeable odor and can be transferred from the plastics that contain it. When burned, DEP produces toxic gases.
Since the compound is a suitable solvent for many organic molecules, it is often used to bind cosmetics and fragrances. Other industrial uses include plasticizers, detergent bases and aerosol sprays. Because of the frequent dermal exposure of humans to the chemical, the question of toxicity is crucial. Several studies suggest that DEP can cause damage to the nervous system as well as to the reproductive organs in males and females.