1. Literally, to attach or connect something to something else. In this usage, a noun or pronoun can be used between "fasten" and "on." I fastened a name tag upon my shirt and walked into the auditorium.
2. By extension, to focus one's attention on someone or something. Luckily, the baby fastened upon the music and stopped crying within minutes.
See also: fasten
fasten (up)on someone or something
1. Lit. to take firm hold of someone or something. She fastened upon me and would not let me go until she finished speaking. I don't like people who fasten on me and ask a lot of questions.
2. Fig. to fix one's attention on someone or something. He fastened upon the picture for a brief moment and then turned away. The baby fastened on the television screen and watched it for many minutes.