The Collaborative International Dictionary of English v.0.48:

Mien \Mien\ (m[=e]n), n. [F. mine; perh. from sane source as
   mener to lead; cf. E. demean, menace, mine, n.]
   Aspect; air; manner; demeanor; carriage; bearing.
   [1913 Webster]

         Vice is a monster of so frightful mien,
         As, to be hated, needs but to be seen.   --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mien
    n 1: dignified manner or conduct [syn: bearing, comportment,
         presence, mien]