noun

• (often mining, waste management) The breaking or grinding up of a material to form smaller particles.
  "He deſcribes in a Mechanical way the manner of its Action; ſuppoſing that ſome of its Particles having undergone ſeveral Comminutions (tho not a Diſſolution) from the various Firments they have paſſed, arrive at laſt, with the Blood, at the Brain; […] thoſe of them, which are not ſmall enough to paſs thoſe Straits along with the Juice, being juſt admitted, ſtick there till other appelling Subſtances give them a farther Comminution, and ſo pretrude them along: […]"
• (traumatology) The fracture of a bone site in multiple pieces (technically, at least three); crumbling.
  "Comminution of the shaft of one or of both bones of the fore-arm does not of itself indicate operative interference, other complications may necessitate primary or secondary amputation."