Immature (Adjective)

(used of living things especially persons) in an early period of life or development or growth; "young people".

All adjective clusters.

Characteristic of a lack of maturity; "immature behavior".

All adjective clusters.

He acted like a spoiled child when he didn't get his way, which is just another example of his immature behavior.
His colleagues avoided him at the office because of his tendency to throw tantrums whenever he disagreed with someone.
Her habit of blaming everyone else for her own mistakes is really immature and something she needs to work on.
It was obvious that the immature manner in which the comedian poked fun at serious issues had crossed a line and alienated a large part of his audience.
Their lack of impulse control and impulsive decision-making are symptoms of immature psychological development that may benefit from therapy.