What’s the meaning of this sign?

Explanation: This sign gives you an early warning that the road ahead will slope downhill. Prepare to alter your speed and gear. Looking at the sign from left to right will show you whether the road slopes uphill or downhill.

Category: Road and traffic signs (Motorcycle Theory 2021)

References: The Official DVSA Guide to Riding: Section 7, Highway Code: Page 108, Know Your Traffic Signs: Page 12