unionize /ˈjuːnjənaɪz/verb 1/ʌnˈaɪənaɪz/ verb 3forms 3 verb1 •To organize workers into a trade union.The company laid off all the workers when they tried to unionize.My uncle got roughed up by some corporate thugs after they caught him trying to unionize their workers. unionize /ʌnˈaɪənaɪz/ verb3 •(rare) To cause (an ionized substance) to return to a neutral state; to convert (an ion) into a neutral atom or molecule. •(rare) Of an ionized substance, to return to a neutral state. •(rare) Synonym of deionize. formsunionized · unionizing · unionizes