1 C1 neutral
Of an engine or rotating machine, to gradually decelerate after power is reduced
"After the pilot shut off the fuel, the engines began to spool down slowly."
inseparable
spool down
C1 neutral inseparable transitive/intransitive
Of a motor, engine, or spinning mechanism, to decelerate and come to a stop
In plain English
When an engine or spinning machine gradually slows down and stops
What does "spool down" mean?
2 meanings, ordered from most common to least. Color-coded by CEFR level.
2 C1 neutral
Of a computing or electronic system, to reduce its operational speed or activity
"The server was instructed to spool down to conserve energy during off-peak hours."
inseparable
Literal vs figurative
Words literally mean
To unwind a spool in a downward/slowing direction — mostly transparent in technical contexts
Actually means
When an engine or spinning machine gradually slows down and stops
Usage tip
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.
Words that pair with "spool down"
Natural word combinations native speakers use most often.
engine turbine rotor drive jet system
How to conjugate "spool down"
The five tense forms you'll use most often.
Base
spool down
I/you/we/they
3rd person
spools down
he/she/it
Past simple
spooled down
yesterday
Past participle
spooled down
have + pp
-ing form
spooling down
continuous
Hear "spool down" in the wild
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Other ways to say "spool down"
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