thiopental UK /ˌθʌɪ.əʊˈpɛn.təl/US /ˌθaɪ.oʊˈpɛnˌtɔl/ noun1 •A barbiturate C₁₁H₁₈N₂O₂S (trademark Pentothal) used in the form of its sodium salt especially as an intravenous anesthetic; and as a supposed truth serum.
