Acronym, standing for Too Late Chum.
An attack by some rock hard warry-types against an entrenched ennemie du jour. The enemy MG position has been blazing away all afternoon, and has hit a few people, but not too many cos the gunner's pants. The lead section gets there first. With about 20m to go to the position, the baddie looses off the rest of his belt of MG ammunition, and puts his hands up.
So, what happens next?
1. The lead warry-guy, in the middle of a firefight, immediately takes the gunner prisoner, jeopardising the lives of many of his comrades from the remaining enemy?
This is a clear-cut case of Too Late Chum, and I'll leave the educated reader to work out which option that means...