What does it mean to be emotionally immature?

Colloquially this may be used as a jab, but in the world of psychology emotional immaturity is a real phenomenon — it is the stunted, contorted, or distorted emotional body of an individual whose life circumstances forced them to develop in unnatural ways.

This distortion and abuse of the emotional body has real consequences represented by harmful behaviors towards others: exaggerated responses to benign circumstances, the inability to understand and respect others' points of view (an undeveloped theory of mind), the dismissal of others' experiences with pithy axioms, the avoidance of intimacy or confrontation, and a cornucopia of other behavioral maladies.

I've gleaned this information from the book Adult Children of Emotionally Immature Parents by Lindsay C. Gibson. Her insights are candid and in plain language. I look forward to deepening my understanding of emotional immaturity through her lens.