1. Or: crush on / heavy crush (on) , an intense or sudden romantic infatuation, often short-lived, towards another person who, often, is unaware of it or does not respond to it; a one-sided infatuation. See love for synonyms.
Quotes:
(1) Elsa Carrington (Madeleine Carroll) to Richard Ashenden (John Gielgud) in Secret Agent (1936): ' I fell in love with you at first sight; not a crush but a crash.'
(2) Nathaniel Mayweather (Charles Elliott) and Trina (Melora Walters) in Cabin Boy (1994): -- Nay: ' Did I mention I have an incredible crush on you? ' -- Trina: ' That's wonderful. I'm always flattered when a psychotic becomes smitten with me.'