United Kingdomian adjective 1noun 1forms 3 adjective1 •(rare) Of, from or relating to the United Kingdom.I don't think asking him will do any good. Isn't he English, or at least Great British (United Kingdomian)? He'll only confuse matters with an entirely different vocabulary. — 2000 noun1 •(rare) A native or inhabitant of the United Kingdom.George Mikes, a Hungarian who became a naturalized United Kingdomian, peeved about that phenomenon in _How to Be an Alien_ some decades back. — 1999 formsUnited Kingdomians · more United Kingdomian · most United Kingdomian