1.
In a battle, the rearguard is a group of soldiers who protect the back part of an army, especially when the army is leaving the battle.
N-SING: the N
2.
If someone is fighting a rearguard action or mounting a rearguard action, they are trying very hard to prevent something from happening, even though it is probably too late for them to succeed. (JOURNALISM)
Mr Urban looks increasingly like someone fighting a rearguard action to keep their job.
PHRASE: V inflects