'buttoned-up' definitions:

Definition of 'buttoned-up'

(from WordNet)
adjective
(British colloquial) not inclined to conversation
adjective
Conservative in professional manner; "employers are looking for buttoned-up types"

Definition of 'buttoned-up'

From: GCIDE
  • 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]