Definitions of vague:

• adjective:   not clearly understood or expressed

  Example: "Their descriptions of human behavior become vague, dull, and unclear- P.A.Sorokin"

• adjective:   not precisely limited, determined, or distinguished

  Example: "Vague feelings of sadness"

• adjective:   lacking clarity or distinctness

  Example: "Saw a vague outline of a building through the fog"