ionizePronunciation: /ˈʌɪənʌɪz/ (also ionise)Definition of ionize verb [with object] convert (an atom, molecule, or substance) into an ion or ions, typically by removing one or more electrons. [no object] become converted into an ion or ions; undergo ionization. Derivatives ionizable adjective ionization noun ionize in other Oxford dictionaries Definition of ionize in the US English dictionary