Plain English Meaning
Adding too much power for what you're trying to do, so the airplane does more than you wanted — climbs faster, speeds up, or pitches up — and you have to fix it.
Full Definition
To apply more engine power than the current flight condition or procedure calls for, causing the aircraft to deviate from the intended performance — typically resulting in unwanted climb, acceleration, or pitch change that the pilot must then correct.
Context Anchor
Seen in instrument flying when setting power to hold a , , climb, , or .