What is Fanglomerate?

Fanglomerates are poorly sorted, matrix-rich conglomerates that originated as debris flows on alluvial fans and likely contain the largest accumulations of gravel in the geologic record.
In simple words, we can say, Fanglomerate is cemented alluvial Fan. whereas an alluvial Fan is a triangle-shaped deposit of gravel, sand and even smaller pieces of sediment. Such as silt.