I forfeited my cell phone to the teacher.
When you obtain something acting like that person had died, it's called confiscation or forfeiture. Maybe if they were alive, you think, they wouldn't have let me take it. Well they are still alive so it's theirs and you can't keep it forever.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.