Definition of bonus genius in US English:

bonus genius

noun

archaic, literary
  • A benevolent spirit imagined as accompanying a person throughout his or her life and exerting a good influence, and often paired with an opposed malevolent spirit.

Origin

Early 17th century. From post-classical Latin bonus genius from classical Latin bonus good + genius.

Pronunciation

bonus genius

/ˌbəʊnəs ˈdʒiːnɪəs/