1. To coordinate the structure of the various parts of something: While drinking a cup of coffee in the morning, Grace started to organize the activities of the day.

Ginny had so many records that were all mixed up, so she started to organize them according to their composers.

2. To establish or to bring into existence: The union leaders were organizing a strike demanding better wages to take place the following week.
3. To arrange for or to make plans: Tim and Jeff wanted to organize their hiking trip, so they had to make train reservations, buy hiking shoes and backpacks, and make sure that the neighbors would look after their homes during the time they were away.