Douglas Harper's Etymology Dictionary
Wiktionary
n. 1 The material that has been used to refill an excavation. 2 (context US English) Reserve support personnel. 3 (context US English) That which backfills; a replacement. 4 (context literature English) Material in a story set earlier in the past, providing history or context for the current action. vb. 1 To refill a hole with the material dug out of it. 2 (context archaeology English) 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. 3 (context US English) To provide reserve support. 4 (context US English) To replenish or restock due to attrition or loss.
Usage examples of "backfill".
He had a single air-tank rig on with a full facemask, because, below the main deck, the mothballed battlewagon had been backfilled with nitrogen gas to displace all the oxygen.
Then they drove a horizontal passage beneath the presumed bottom of the original Water Pit, where they found cribbing and the continuation of the original backfilled shaft.
Resuming the dig, they soon reached a number of heavy vertical oak beams and cross-joists, which appeared to be the ancient cribbing of a backfilled shaft.
Tiber rose just enough to ensure that some of the public latrines backfilled and floated excrement out of their doors, a vegetable shortage developed when the Campus Martius and the Campus Vaticanus were covered with a few inches of water, and shoddily built high-rise insulae began to crumble into total collapse or suddenly manifested huge cracks in walls and foundations.
We drove reinforcing rods into the ground in each tube and then backfilled the holes around the tubes.
Each cracking thud of pick or shovel had a purging effect on them, and in the end, backfilling the graves over the bare bodies, together they came out of their pain and into a new, more barren reality.
With a reflector, some backfill, a diffuser, she could have made this shot sing.