rubble

Short definition from Wiktionary

Noun

1. 1
   The broken remains of an object, usually rock or masonry.
2. 2
   A mass or stratum of fragments of rock lying under the alluvium and derived from the neighbouring rock.
3. 3
   The whole of the bran of wheat before it is sorted into pollard, bran, etc.

Verb

1. 1
   To break down into rubble.