Another very British one - which doesn't mean the same, although it's related in that it is emotionless - is keeping 'a straight bat' (a reference to a safe cricketing stroke).
Has anyone mentioned "to keep a straight face" or "Jimmy Carter is a great man?" Oh, only the former is relevant. Oh well.
The expression often used in American newspapers and on the news is: stone-faced.
i.e. The defendant sat stone-faced in the courtroom as the verdict was read.
The expression: without batting an eye is also used sometimes. This means you do something and do not even blink your eyes to indicate any type of feeling. The criminal pointed his gun at the teller and, without batting an eye, she told him to go to hell.
That reminds me of a cliche often used in sports commentaries: 'Fergusson sat tight-lipped and ashen-faced as his team had rings run round them'. It's clear that he's not happy, but he doesn't react in a way that would give more specific information about what's making him unhappy.
Last edited by BobK; 13-May-2011 at 18:28. Reason: Added last sentence
Last edited by BobK; 21-May-2011 at 13:36. Reason: added last paren