1) Accumulation 2) The act of cumulating 
• (n.) The act of heaping together; a heap. See Accumulation.
In an anti-dumping case against imports from more than one country, the summation of these imports for the purpose of determining injury. That is, the imports are deemed to have caused injury if all of them together could have done so, even if individually they would not.
Cu`mu·la'tion noun [ Confer French cumulation .] The act of heaping together; a heap. See Accumulation . 
the act of cumulating; accumulation. · a heap; mass.
a collection of objects laid on top of each other