To Decide
To Determine
する verb
A 決定 is a "decision." So, when you add する to it you're making it a verb, meaning this word means to decide.
The reading is the same as 決定 with する added. Make sure you know 決定 and you'll know this word as well.
コウイチの赤ちゃんの名前が決定したら、すぐにお知らせしますね。
Once they've decided on a name for Koichi's baby, I'll let you know right away.
コンテストの勝者を決定しました。
The winner of the contest has been decided.
クソワロタwwwこのテレビ番組クソほどおもしろいじゃねーかよ。俺の一番好きな番組に決定したわ。
ROFL! This TV show is hilarious, man. I’ve decided that this is now my new favorite show.