Have a crush (on someone)
American SlangDefinition
To feel a strong, often secret, romantic infatuation or attraction toward someone, typically light or short-term.
Examples
"I’ve had a crush on my lab partner all semester, but I’m too shy to tell her."
"He admitted he used to have a crush on his neighbor when they were kids."
"Everyone can tell she has a crush on the new guy at work—she gets all giggly when he walks by."