/ ˈwɔːnɪŋ; NAmE ˈwɔːrn-/ noun
1.
[ C , U ] a statement, an event, etc. telling sb that sth bad or unpleasant may happen in the future so that they can try to avoid it :
Doctors issued a warning against eating any fish caught in the river.
to give sb fair / advance / adequate warning of sth
The bridge collapsed without (any) warning .
Let me give you a word of warning .
a government health warning
—see also early warning
2.
[ C ] a statement telling sb that they will be punished if they continue to behave in a particular way
SYN caution :
to give sb a verbal / written / final warning
► warn·ing adjective [ only before noun ]:
She had ignored the warning signs of trouble ahead.
Police fired a number of warning shots .
Warning bells began to ring (= it was a sign that sth was wrong) when her letters were returned unopened.
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WORD ORIGIN
Old English war(e)nung (see warn , -ing ).