Meaning
Feeling mildly ill, run-down, or not quite well, physically rather than emotionally.
It’s a soft, understated way of reporting sickness — used for a minor cold or general low energy rather than a serious condition.
Origin
The most commonly cited explanation is nautical: a sailor who felt seasick or unwell was sent below deck, away from the “weather” side of the ship — the side facing the wind and rough seas — and out of the elements, so that being genuinely “under the weather” (below deck, out of the storm) came to describe feeling unwell in general. That story fits naturally with a cluster of other sea-derived English weather vocabulary, though pinning down its exact earliest use is difficult; a clearly documented American usage for illness appears in Andy Adams’s 1907 novel “Reed Anthony: Cowman” (“a quiet little man, who also had been under the weather from malaria”), by which point the phrase was already established enough to be used without any explanation.
Examples
I’m feeling a bit under the weather today, so I’ll skip the gym.
She’s been under the weather since Monday.
He sounded under the weather on the phone.
A: Where’s Tom? B: He’s home, a bit under the weather.
Frequently asked questions
What does 'Under the weather' mean?
Feeling mildly ill, run-down, or not quite well, physically rather than emotionally.
It’s a soft, understated way of reporting sickness — used for a minor cold or general low energy rather than a serious condition.