A misfortune.

The use of ‘ill wind’ is most commonly in the phrase ‘it’s an ill wind that blows nobody any good’. This is first recorded in John Heywood’s A dialogue conteinyng the nomber in effect of all the prouerbes in the Englishe tongue, 1546:

“As you be muche the worse. and I cast awaie.
An yll wynde, that blowth no man to good, men saie.
Wel (quoth he) euery wind blowth not down the corn
I hope (I saie) good hap [luck] be not all out worn.”