1. Of liquid, to accumulate into a pool. It turns out that rain water had been pooling up under the foundations, causing a massive amount of damage to the property.

2. To gather up, accumulate, or group together something, especially money or other resources, from various places or sources. In this usage, a noun or pronoun can be used between "pool" and "up." We've all been pooling our money up to buy these lottery tickets, so we all deserve equal shares of the winnings! The four companies came together pooled up their top legal teams to sue the government over the new law.