What does it mean for an aircraft to be trimmed?

An aircraft is trimmed when it is in equilibrium with all forces and moments balanced, requiring no pilot control input to maintain the current flight condition. Trim involves adjusting control surfaces (or tabs) so lift equals weight, thrust equals drag, and all moments sum to zero. Trim speed/attitude changes with CG position, flap setting, and power. Trim tabs or electric trim systems relieve the pilot from constant control forces. Proper trim is essential for hands-off flight and reduces pilot workload. Mistrim creates persistent control forces.