Entry 1 sense Webster, 1913 Illegalize · Il·le·gal·ize · IPA /ɪˈliːɡəlʌɪz/ 01 v. t. To make or declare illegal or unlawful. imp. & p. p. Illegalized; p. pr. & vb. n. Illegalizing 1. To make or declare illegal or unlawful.