noun which may take the genitive case particle 'no', noun
transient; temporary; passing; fleeting
Often used in medical or technical contexts for symptoms or phenomena that appear briefly and then disappear. Can also describe general short-lived states.
この症状は一過性のもので、すぐに治まります。
This symptom is transient and will subside quickly.
一過性の流
I think it's just a passing fad.
Compound of 一 (one, single), 過 (pass, exceed), and 性 (nature, property). Literally 'one-pass nature', referring to something that occurs once and then passes.