2. A distressing or difficult circumstance or situation: "She has had troubles ever since she took this job."
3. A cause or source of distress, disturbance, or difficulty: "The new students were a trouble to the teacher."
4. A condition of pain, disease, or malfunction: "Her father had both heart trouble and car trouble."
5. Public unrest or disorder; a disturbance.
6. Something that is extremely difficult or which presents a problem.
Origin of the word, "trouble"
When a person is in trouble, his or her mind is ill at ease. The Latin parent of the word trouble indicates the same thing because turbo meant "disturb".
It came into English first with the spelling turble, then truble, and finally trouble. This same Latin word, turbo, has given us turbulent, "full of commotion"; disturb, "throw into complete disorder", and turbid, or in other words, a turbid stream which is "all muddied up."