dirty spot

基本解释

Moreover, it is not a local dirty spot but the whole lake is polluted.
除此之外，脏的并不是局部，而是整个湖泊都被污染了。
The law is like a mirror which can show us a dirty spot on our face but the mirror can't wash it off.
律法就如一面镜子，反照出我们脸上的污秽，但镜子却不能把污秽除掉。
It is analyzed that electrode surface sticks dirty spot unevenly and electric field varies irregularly during welding the phosphorized weldment by 3-phase DC projection welder secondary rectification.
分析了三相次级整流凸焊表面磷化构件时，产生电极表面不均匀粘污，从而引起电流场发生畸变的原因。

The idea is that the vaccines will train T cells to spot cancer, while the antibody will make sure the T cells remain activated long enough to do their dirty work.
FORBES: Magazine Article