General
check six
What does check six mean?
An exhortation to watch one's back. From aviation, where the clock positions describe directions and 'six o'clock' is directly behind the aircraft.
"Stay sharp and check six out there."
Origin
US military aviation slang, from clock-position bearings.
Frequently asked questions
What does 'check six' mean?
It means watch behind you and guard your rear — a warning to stay aware of threats coming from directly astern.
Why 'six'?
It comes from aviation clock-position bearings, where twelve o'clock is straight ahead and six o'clock is directly behind the aircraft.
Is 'check six' only used by pilots?
It started in aviation but is now used broadly, even figuratively, to tell someone to watch their back.
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