IPA: /ˈmɑːr.plɒt/
KK: /mɑrˌplɑt/
A person who interferes in a situation, often causing problems or ruining plans due to their meddling behavior.
His constant interruptions made him a marplot in the team's efforts to complete the project on time.
Marplot is derived from the phrase 'to mar the plot', where 'mar' (from Old English 'merran', meaning to spoil or damage) means to spoil, and 'plot' (from Old French 'plote', meaning a plan or scheme) refers to a scheme or plan. The term describes someone who spoils or disrupts a plan or scheme.
Think of someone who 'spoils' ('mar') a 'plan' ('plot') — that's why a marplot is someone who disrupts or ruins a scheme.
No commonly confused words.