1. A process by which something increases in amount or is collected together over time: "When a person continues to put money into a bank account, the amount that builds up is the accumulation of his or her savings."

"If it is an interest bearing account, the interest will make the accumulation even larger."

2. Several things that are grouped together or which are considered as a whole.
3. The act of gathering or amassing, as into a heap or pile: "The accumulation of leaves blocked the drain pipe from the roof of the garage."