The pinocytosis (alternative spelling: Pinocytose) refers to the active water uptake of a cell by invagination of the cell membrane. The liquid does not diffuse through the membrane, but arrives in a cell bounded by the membrane transport vesicle.
Synonymous with the term pinocytosis (from the Greek 'pino' = drink; 'kytos' = envelope), the terms hydrophagocytosis or 'cell drinking' are sometimes used. Pinocytosis is one of two processes in the context of endocytosis, ie the uptake of substances from the extracellular space. Upon ingestion of particles, and not just water, with the particles released therein, it is called phagocytosis.