1 [uncountable and countable]MI
an illness or a medical condition in which you have a very high temperature:
Andy has a fever and won't be coming into work today.
I woke up this morning with a fever and an upset stomach.
She's running a fever (=has a fever).
a high/low/slight fever➔ hay fever, scarlet fever, yellow fever, glandular fever, rheumatic fever
The usual symptoms are a pink rash with a slight fever.
a situation in which many people feel very excited or feel very strongly about something
a fever of excitement on Wall Street
election/carnival etc fever (=great interest or excitement about a particular activity or event)
Soccer fever has been sweeping the nation as they prepare for the World Cup.
3 British English
if people's feelings are at fever pitch, they are extremely excited:
The nation was at fever pitch in the days leading up to the election.
After a night of rioting, tensions in the city reached fever pitch.