To pretend you are not interested in someone to make them feel interested in you
Play hard to get
To be in love with someone in an out-of-control way
Be head over heels
To be secretly in love with someone
Have a crush on someone
To get married
Tie the knot
To be strongly attracted to someone
Have chemistry with someone
An unreasonable passion for someone you don't know very well, generally based on physical attraction
Be infatuated with someone
Not to meet someone you had arranged to see
Stand someone up
To be having a relationship with someone
Be seeing someone
To desire someone
Drool all over someone
To be interested in someone
Be into someone
To be unfaithful to a partner
Cheat on someone
To invite someone on a date
Ask someone out