a final offer issued in negotiations, the rejection of which can lead to a break in relations and some action
undercarriage
the part of a plane, including the wheels, that provides support when it is on the ground and when it is landing or taking off
unexploded ordnance
any sort of military ammunition or explosive ordnance that has failed to function as intended
United Kingdom (UK)
refers to the United Kingdom of Great Britain and Ireland from 1 January 1801 to 5 December 1922, or the United Kingdom of Great Britain and Northern Ireland from 5 December 1922
upper class
describes a group of people in a society who have the highest economic or social status
