Definition of Brexiter in US English:

Brexiter

noun

British
informal
  • A person who is in favor of the United Kingdom withdrawing from the European Union.

    ‘many Brexiters would like to follow the Norwegian model’
    ‘this was not another scary intervention in the referendum debate by a pro-European or a Brexiter’

Origin

Early 21st century: from Brexit + -er.

Pronunciation

Brexiter

/ˈbreksədər//ˈbrɛksədər/