A decision, agreement, or rule; can also refer to a decisive action or point. It is also used as a suffix in compound expressions.
会議で今後の進め方の決めをした。
We decided how to proceed at the meeting.
演技のラストは決めのポーズで締めた。
The performance ended with a finishing/striking pose.
試合の流れを変えたのは彼の決めのシュートだった。
The shot that changed the course of the game was his decisive shot.