a very high degree; extreme; utmost (used to indicate an extreme state or degree).
彼は極度の緊張で声が震えていた。
He was shaking with extreme nervousness.
極度に疲れていたので、早く寝た。
I was extremely tired, so I went to bed early.
その薬は極度の副作用を引き起こすことは稀だ。
It is rare for that medicine to cause extreme side effects.