If something is unconstitutional, it breaks the rules of a political system.
例句
The Moldavian parliament has declared the elections unconstitutional...摩爾達維亞議會已宣布選舉違憲。Banning cigarette advertising would be unconstitutional, since selling cigarettes is legal.既然出售香煙是合法的，那么禁止做香煙廣告就是違憲的。
英漢詞典釋義
adj.
違反憲法的,不符合章程〔法規〕的
The prospect for passage of the bill was somewhat cloudy,in view of its evident unconstitutionality.由于這個議案明顯地違反了憲法,它能否得到通過的前景就有點不明顯了。
英英詞典釋義
Adjective
1. not consistent with or according to a constitution; contrary to the U.S. Constitution