To make the effort or go out of one's way (to do something). Usually followed by "to do something" or "of doing something." Oh, you didn't have to take the trouble of preparing the guest bedroom for me—I could have just slept on the couch! Your father took the trouble to cook this delicious meal, and now you are going to sit down and eat it! Thank you for the detailed instructions you wrote out for me, but you shouldn't have taken the trouble—I could have just looked it up on my phone!