Definitions

1. noun

A gear ratio or set of gears that allows a vehicle to travel at a slower speed than normal when the engine is in high gear, often used to assist in hill climbing or to reduce engine speed.

“The underdrive feature helped us navigate the steep mountain roads safely.”

2. verb

To drive at a slower speed than normal, especially when ascending a hill or navigating difficult terrain.

“We had to underdrive the vehicle to avoid getting stuck in the mud.”

3. adverb

At a slower speed than normal.

“The vehicle underdrives up the steep hill with ease.”