To play a violin or similar instrument. She fiddled beautifully at the concert last night.
To touch or manipulate something in a nervous or restless way. He fiddled with his pen while waiting for the interview to start.
To make small adjustments to something, often in an attempt to improve it. He fiddled with the engine until it started running smoothly.
To waste time or engage in aimless activity. She fiddled around all afternoon instead of doing her homework.
To falsify or tamper with something, especially in a dishonest way. The accountant was caught fiddling the books to hide the losses.