un·as·ser·tive /ˌʌnəˈsɚ/
  (a.)不武斷的,謙虛的,害羞的
  unassertive
       adj 1: inclined to timidity or lack of self-confidence; "a shy
              unassertive person" [ant: assertive]
       2: not blatant or overly aggressive in manner or appearance; "a
          retiring disposition" [syn: retiring]