[jí shǒu]
thorny; troublesome; knotty; difficult to handle
a knotty [thorny] problem; the Gordian knot; a matter full of knots
棘手的问题
This is a sticky business.
这件事情很棘手。
When others interfere in the affair, it always makes troubles.
别人一卷入这一事件，棘手的事情就来了。