/ ˈsɪknəs; NAmE / noun
1.
[ U ] illness; bad health :
She's been off work because of sickness.
insurance against sickness and unemployment
➡ note at illness
2.
[ U , C , usually sing. ] a particular type of illness or disease :
altitude / travel / radiation, etc. sickness
—see also sleeping sickness
3.
[ U ] ( especially BrE ) the feeling that you are likely to vomit (= bring food back up from the stomach to the mouth) ; the fact of vomiting
SYN nausea :
symptoms include sickness and diarrhoea
The sickness passed off after a while.
—see also morning sickness
4.
[ sing. ] a feeling of great sadness, disappointment or disgust
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WORD ORIGIN
Old English sēocnesse (see sick , -ness ).