rearguard

adjective

1. of or relating to a rear guard.
2. designed to oppose or prevent in a defensive way: a rearguard strategy.

noun

1. a detachment detailed to protect the rear of a military formation, esp in retreat
2. an entrenched or conservative element, as in a political party
3. rearguard action
   1. an action fought by a rearguard
   2. a defensive action undertaken to try to stop something happening or continuing