As a Noun:
1. The inability to understand or learn things easily or be unable to plans things well. English = ignorance.
2. The inability to use your experience and knowledge in order to make sensible decisions and judgements. English = inexperience, immaturity.
3. A person who is unable to understand or learn things easily, or to use their experience and knowledge in order to make sensible decisions and judgements. English = simpleton, ignoramus.
As a Verb or Adjective:
1. To not understand or learn things easily or be unable to plan things well. English = (be) dim witted, (be) ignorant, (be) uneducated.
2. To be unable to use your experience and knowledge in order to make sensible decisions and judgements. English = (be) ill-informed, (be) inexperienced, (be) unwise.