Plain English Meaning
A scale with regular tick marks and numbers on it, like a ruler, that lets you read off an exact value. On a compass, it is the ring of degree markings you read to see which way the aircraft is pointing.
Full Definition
A measuring surface marked with a series of evenly spaced lines and numbers used to read a value directly. On a magnetic compass, it is the printed scale around the compass card showing headings in degrees from 0 through 359, usually marked every 5 degrees with numerals shown every 30 degrees.
Context Anchor
Seen on the magnetic compass when reading or checking the airplane’s compass direction.
Derivation
From Latin gradus, meaning 'step.' A graduated scale is literally a scale built in steps -- evenly spaced increments you can count along.
Why Pilots Care
Enables accurate determination of aircraft heading without estimation or guesswork.
Analogy
Like the markings on a ruler or a kitchen measuring jug -- the value you want is read directly off the line nearest the pointer.
Intuition Check
“Graduated” does not mean finishing school here, and “scale” does not mean a weighing device. In this context, a graduated scale means a set of measurement marks divided into steps.
Example Sentence 1
The pilot read 270 degrees off the graduated scale on the compass card, confirming a westerly heading.
Example Sentence 2
During the compass swing, the technician verified each marking on the graduated scale against known headings.