Unconstitutional means against the basic law of a country. Ruled unconstitutional, an unconstitutional act, plainly unconstitutional.
In countries with a written constitution a court can strike a law down as unconstitutional, which is real power. Britain has no single document, so the word is used politically rather than legally there.
1adjectiveunconstitutionalAgainst the basic law of a country.
“Critics argued that closing parliament for months would be unconstitutional.”
unconstitutional is a quality.
Proto-Indo-European
*steh₂- — to stand (up)
Latin
cōnstitūtiō
Old French
constitucion
Middle English
constitucioun
English
constitutional
English, today
unconstitutional
Built from
From un- + constitutional. constitutional comes from constitution + -al. Constitution is derived from Middle English constitucioun, constitucion (“edict, law, ordinance, regulation, rule, statute; body of laws or rules, or customs; body of fundamental principles; principle or rule (of science); creation”) from Old French constitucion (modern French constitution), a learned borrowing from Latin cōnstitūtiō, cōnstitūtiōnem (“character, constitution, disposition, nature; definition; point in dispute; order, regulation; arrangement, system”), from cōnstituō (“to establish, set up; to confirm; to decide, resolve”) (from con- + statuō (“to set up, station; to establish; to determine, fix”) (ultimately from Proto-Indo-European steh₂- (“to stand (up)”))) + -tiō, -tiōnem.
Etymology from Wiktionary, CC BY-SA