noun which may take the genitive case particle 'no', na-adjective, noun
exceptional; unprecedented; unusual
Describes something that deviates from normal practice or precedent, often in formal or news contexts. Can be used as a noun, no-adjective, or na-adjective.
これは異例の措置だ。
This is an exceptional measure.
It was an unusually quick decision.
The government took an unprecedented measure.
He was promoted at an unprecedented speed.
This ruling is said to be unprecedented.
異例 means 'unprecedented/exceptional', focusing on breaking from precedent, while 特殊 simply means 'not general or standard'.