Question 1

What does "spool down" mean?

Accepted Answer

Of an engine or rotating machine, to gradually decelerate after power is reduced

Question 2

How do you use "spool down" in a sentence?

Accepted Answer

After the pilot shut off the fuel, the engines began to spool down slowly.

Question 3

Is "spool down" formal or informal?

Accepted Answer

"spool down" is register-neutral — appropriate in both casual and formal contexts. Technical term used in aviation, computing, and engineering. Refers to the gradual deceleration of a spinning system such as a jet turbine or hard drive. The opposite is 'spool up.' Can also be used transitively ('spool down the engine'). Not common in everyday speech.

spool down

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