BCR

A MLA meaning Battle Casualty Replacement.

There's a cheery prospect. You're here to take over from a bloke who was injured or killed.

It was for a period renamed to ITR (In Theatre Reinforcement), in the hope that it would sound a bit better (same outcome though - you're standing by waiting to take over from a bloke with a hole in him, at which point you'll get redeployed to a place known to be somewhat hot)

Find out more in the Dictionary