1 [count] : a part or step in a process : one part in a series of related events or actions
▪ The project will be done in three phases. ▪ He's in the final phase of treatment now. ▪ The building project marks a new phase in the town's development. ▪ These poems are from an early phase [=stage] in her career. 2 [count] : a short period of time during which a person behaves in a particular way or likes a particular thing
▪ He has been throwing tantrums a lot, but the doctor says it's just a phase. ▪ She's going through a punk phase right now. [=she likes punk music and fashion at this point in her life] 3 [count] : the shape of the part of the moon that is visible at different times during a month
▪ a calendar based on the phases of the moon 4 [noncount] Brit : the state in which things work together with each other — used in the phrases in phase or out of phase ▪ Make sure the machine's wheels are moving in phase with each other. ▪ The sound on this movie is out of phase. [=the sound does not match the images of the movie] ▪ He seems to be out of phase [=(US) out of step] with the rest of the team.