tetrahydrocannabinol UK /ˌtɛ.tɹəˌhʌɪ.dɹə(ʊ)ˈkæn.əb.ɪn.ɒl/US /ˌtɛ.tɹəˌhaɪ.dɹək.əˈnæb.əˌnɔl/ noun1 •The psychoactive substance present in cannabis, a hydrogenated derivative of cannabinol. formstetrahydrocannabinols