gremlin
noun [ C ] uk/ˈɡrem.lɪn/ us/ˈɡrem.lən/
（尤指想象中钻到机器里面使其出现故障的）小妖精
an imaginary little creature that gets inside things, especially machines, and makes them stop working
We must have a gremlin in the engine - it isn't working right. 发动机里一定是钻进去了个小妖精——现在运转不正常了。