Unconstitutional \Un*con`sti*tu"tion*al\, a. Not constitutional; not according to, or consistent with, the terms of a constitution of government; contrary to the constitution; as, an unconstitutional law, or act of an officer. --Burke. -- {Un*con`sti*tu"tion*al"i*ty}, n. -- {Un*con`sti*tu"tion*al-ly}, adv.