The Collaborative International Dictionary of English v.0.48:

Accumulation \Ac*cu`mu*la"tion\, n. [L. accumulatio; cf. F.
   accumulation.]
   1. The act of accumulating, the state of being accumulated,
      or that which is accumulated; as, an accumulation of
      earth, of sand, of evils, of wealth, of honors.
      [1913 Webster]

   2. (Law) The concurrence of several titles to the same proof.
      [1913 Webster]

   Accumulation of energy or power, the storing of energy by
      means of weights lifted or masses put in motion;
      electricity stored.

   An accumulation of degrees (Eng. Univ.), the taking of
      several together, or at smaller intervals than usual or
      than is allowed by the rules.
      [1913 Webster]