unexpressive \un`express"ive\, a.
   1. not expressive; not having the power of utterance;
      inexpressive.
      1913 webster

   2. incapable of being expressed; inexpressible; unutterable;
      ineffable. obs.
      1913 webster

            run, run, orlando; carve on every tree
            the fair, the chaste and unexpressive she. --shak.
      1913 webster -- un`express"ively, adv.
      1913 webster
see also:
un`express"ively 

unexpressive
     adj : deliberately impassive in manner; "deadpan humor"; "his face
           remained expressionless as the verdict was read" syn:
           deadpan, expressionless, impassive, poker-faced
see also:
deadpan expressionless impassive poker-faced