Masting[1] refers to a mass seeding phenomenon exhibited by some species of plants which can be defined as "synchronous production of seed at long intervals by a population of plants"[2], strict masting only occurs in species that are monocarpic (or semelparous) -- individuals of the species only reproduce once during their lifetime, then die.[3]
Mast seeding happens in a Mast year related to that particular species in that particular region.