haloperidol UK /ˌhæ.lə(ʊ)ˈpɛ.ɹɪ.dɒl/US /ˌhæ.loʊˈpɛ.ɹɪˌdɔl/ noun1 •A synthetic antidepressant drug, with the chemical formula C₂₁H₂₃ClFNO₂, used in the treatment of psychotic conditions. formshaloperidols