Wiktionary
n. (context legal English) A litigant without an attorney.
Wikipedia
A litigant in person is an individual, company or organisation that is not represented in court by a solicitor or barrister, but nevertheless has rights of audience (this is, the right to address the court in person). Instructing a barrister and not a solicitor, for example through the Public Access Scheme, however, does not prevent the party on whose behalf the barrister had been instructed from being a litigant in person.
With the appropriate guidance it is possible for litigants in person to have access to the legal system and achieve victory against even the most well represented opponents.
It is possible nevertheless for litigants in the UK to obtain free legal advice and in some cases representation from the Citizens Advice Bureau (CAB).