Definition of puer aeternus in US English:

puer aeternus

(also puer aeternis, puer eternus, puer eternis)

noun

  • In Jungian psychology: an archetype of eternal youth. Also (more loosely): an emotionally or psychologically childlike man.

Origin

Early 20th century. From classical Latin puer aeternus, after use in a German context by C. G. Jung.