immature

Adjective

• (of birds) not yet having developed feathers
  • a small unfledged sparrow on the window sill
    

• not yet mature

• not fully developed or mature; not ripe
  • unripe fruit
    
  • fried green tomatoes
    
  • green wood
    

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

• characteristic of a lack of maturity
  • immature behavior
    

Related words

• Synonyms: 
  unfledged , green , unripe , unripened , young
• Antonyms: 
  fledged , mature , ripe , old