Strongly interacting massive particle

A strongly interacting massive particle (SIMP) is a hypothetical particle that interacts strongly between themselves and weakly with ordinary matter, but could form the inferred dark matter despite this. Strongly interacting massive particles have been proposed as a solution for the ultra-high-energy cosmic-ray problem and the absence of cooling flows in galactic clusters.

Source: Wikipedia — Strongly interacting massive particle (CC BY-SA 4.0)