ˈmärˌplät noun
Etymology: mar (I) + plot
1. : one who frustrates or ruins a plan or undertaking by his meddling
served by varmints, nitwits, and marplots — S.L.A.Marshall
2. : one who endangers the success of an enterprise
this small marplot had discovered a great deal too much — Rudyard Kipling
• mar·plot·ry -lä.trē noun -es