According to Longman English Dictionary Online, Dictionary.com, Merriam-Webster Online, and The Free Dictionary, brainwave is a synonym for brainstorm.
Longman English Dictionary Online:
Brainwave (British English) a sudden clever idea = brainstorm (American English)
ldoceonline.com/dictionary/brainwave
Can they be used interchangeably in spoken English?
Could you please provide me with an example?
Native speakers of English,… any idea?
Some people frowned on this usage of the word ‘brainstorm’ for a number of years as it has associations with epilepsy in another sense. However, it seems to be becoming acceptable again now.
To me, ‘brainstorming’ is not quite defined like this though. Brainstorming is when a group of people get together to think about ideas/concepts, etc. Initially all ideas are welcomed, regardless of how crazy or implausible they seem. People are encouraged to provide any and every idea they have. Later, the ideas will be accepted or rejected on merit.