Definition of "interloper"

In a button-up plaid shirt with an unwieldly suitcase, he is an interloper from another world – one whose first social faux pas is to make his way slowly through the various gates and arrive at the imposing front door on foot, rather than wait to be picked up from the train station by a servant.

2023 November 13, Rosalind Jana, “Saltburn and the bizarre life of Britain's stately homes”, in BBC‎