- fall deeply and completely in love, especially suddenly.
- madly in love.
- be very much in love with someone.
An idiom that is used to describe great strength of feeling, rather than the start of that feeling is head over heels. If you describe yourself as head over heels (in love) with someone, you mean you are completely in love, with very strong feelings.
- I’m head over heels in love. He’s completely changed my life.
- The actor is reportedly head over heels in love with his co-star.
- Tom and Mary are head over heels in love with each other and are going to get married next month.