spool down
C1 neutral inseparable both
In simple words
When an engine or spinning machine gradually slows down and stops
Literal meaning: To unwind a spool in a downward/slowing direction — mostly transparent in technical contexts
Meanings
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."
Grammar: inseparable
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."
Grammar: inseparable
Usage notes
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.
Commonly used with
engine turbine rotor drive jet system
Forms
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
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Synonyms
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