buttoned-up

from WordNet (r) 3.0 (2006)

buttoned-up
    adj 1: (British colloquial) not inclined to conversation
    2: conservative in professional manner; "employers are looking
       for buttoned-up types"

from The Collaborative International Dictionary of English v.0.48

buttoned-up \buttoned-up\ adj.
   1. taciturn. Opposite of {voluble}. [British colloquial]
      [WordNet 1.5]

   2. conservative in professional manner; as, employers are
      looking for buttoned-up types.
      [WordNet 1.5]