Mesmerizing is defined as capturing and holding someone's attention.(verb)
When a movie captures your attention and you simply cannot look away, this is an example of when the movie is mesmerizing.
The definition of mesmerizing is someone or something so fascinating or interesting that you cannot look away or cannot stop thinking about it.(adjective)
A stunning girl with beauty that makes men stop in their tracks is an example of someone who would be described as mesmerizing.