Definition of amassing:
(v) :
(transitive) to gather a great quantity of; to accumulate.
(v) :
(transitive) To collect into a mass or heap.
(v) :
(intransitive) To accumulate; to assemble.
(n) :
(obsolete) A large number of things collected or piled together.
(n) :
(obsolete) The act of amassing.