Plain English Meaning
The middle leg of an instrument approach. After lining up roughly toward the runway, this is where the pilot gets straight, slows down, and gets ready to start the final descent.
Full Definition
The portion of an instrument approach procedure that connects the initial approach segment to the final approach segment. It begins at the intermediate fix (or intermediate point) and ends at the final approach fix or point. Its purpose is to position the aircraft for the final descent: aligning it with the final approach course, adjusting speed, and completing the landing configuration.