Entry 1 sense Webster, 1913 Parenthesize /(pȧ*rĕn"thē̇*sīz)/ · Pa·ren·the·size · IPA /pəˈɹɛnθ.ə.saɪz/ 01 v. t. To make a parenthesis of; to include within parenthetical marks. 1. To make a parenthesis of; to include within parenthetical marks.