The process whereby fluids pass through a filter or a filtering medium WordNet 3.0 & Open English WordNet

Filtration is a physical separation process that separates solid matter and fluid from a mixture using a filter medium that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as oversize and the fluid that passes through is called the filtrate. Wikipedia

Separating solids from fluids by interposing a strainer, a medium through which only the fluid can pass Wikipedia Disambiguation

Separating components suspended in a fluid based on granularity properties relying on a filter device Wikidata

Separation of suspended particles from a liquid, gas, etc., by the action of a filter. OmegaWiki

The act or process of filtering; the mechanical separation of a liquid from the undissolved particles floating in it. Wiktionary

Filtering. Wiktionary (translation)