Definitions of uncertain:

• adjective:   not safe from danger or mishap

  Example: "Faced an uncertain future"

• adjective:   not firm or secure

  Example: "Balancing three boxes in an uncertain pile"

• adjective:   ambiguous (especially in the negative)

  Example: "She spoke in no uncertain terms"

• adjective:   not established beyond doubt; still undecided or unknown

  Example: "An uncertain future"

• adjective:   lacking or indicating lack of confidence or assurance

  Example: "Uncertain of his convictions"

• adjective:   not certain to occur; not inevitable

  Example: "Everything is uncertain about the army"

• adjective:   not consistent or dependable

  Example: "An uncertain recollection of events"

• adjective:   not established or confirmed
• adjective:   subject to change

  Example: "The weather is uncertain"