adjective (a)

• lacking self-confidence(adj.all)

  Example:
  A very unsure young man.
  

  Synonym:
  diffident, shy, timid
  Antonym:
  confident
  

  source: wordnet30
• lacking or indicating lack of confidence or assurance(adj.all)

  Example:
  Unsure of himself and his future.
  Moving with uncertain (or unsure) steps.
  

  Synonym:
  incertain, uncertain
  Antonym:
  certain, sure
  

  source: wordnet30