Decantation is a process of separation that involves pouring a liquid from one container into another while leaving the insoluble material behind. There are several synonyms for decantation that you can use to describe this process, including separating, pouring off, siphoning, and draining. Separating is a broad term that refers to any method of separating a mixture into its component parts. Pouring off is used when you are carefully pouring a liquid from one container to another in order to leave the sediment or solid pieces at the bottom. Siphoning is the process of using a tube to transfer a liquid from one container to another. Draining is the process of allowing a liquid to flow out of a container by taking out a plug or lifting a valve.