1. a person who spoils or ruins a plan or situation by interfering
Usage: somewhat archaic

Examples

• Don’t invite him to the planning meeting – he’s a real marplot who always finds fault with our ideas.
• The surprise party was ruined by a marplot who accidentally revealed the secret.
• She proved to be a marplot, constantly interrupting the negotiations with unhelpful suggestions.
• The project would have succeeded if not for that marplot spreading doubt among the team.
• His reputation as a marplot made others hesitant to include him in their schemes.
• The well-meaning but clumsy marplot managed to upset all their carefully laid plans.