backfill

verb

1. To refill a hole with the material dug out of it.

   “Clay excavated for the new river channel has been used to backfill the old watercourse, while embankment vegetation was also moved from the old channel to the new in order to preserve a habitat for the rare Four Spotted Moths that live there.”

2. To refill an excavation unit to restore the former ground surface and/or to preserve the unit and make it recognizable as having been excavated.

   “We backfilled the cistern with pea gravel to discourage its use as a refuse container.”

3. (US)To provide reserve support.
4. (US)To replenish or restock due to attrition or loss.

   “The company backfilled Joe's position after he was terminated.”

5. To enter an online game that's already in progress, replacing a player who left early.

noun

1. (countable, uncountable)The material that has been used to refill an excavation.
2. (US, countable, uncountable)Reserve support personnel.
3. (US, countable, uncountable)That which backfills; a replacement.
4. (countable, uncountable)Material in a story set earlier in the past, providing history or context for the current action.