Use the term jamais vu when something happens which seems like it should be familiar but isn’t. Some medical conditions can cause a sense of jamais vu in patients.
Someone who doesn’t recognize quite ordinary or familiar things — or people — suffers from a sense of jamais vu. You’re most likely to hear about jamais vu from a psychologist or student of psychology, since researchers have observed people with epilepsy, amnesia, and other conditions suffer from an eerie feeling that they should recognize something that seems brand new to them. The opposite of jamais vu is déjà vu, the vivid sense you’ve experienced something before.