1. organise or arrange details of event or project
plan out the party/meeting/conference
To 'plan out' something means to carefully plan or arrange how you are going to do something or make a detailed itinerary of how you want something to go in the future. "I have my birthday party all planned out." "I have planned out how I am going to get my dream job." "We have our approach planned out." You will hear this expression used both in social and professional contexts.