What term is used for the process of engulfing smaller organisms or food particles?

Phagocytosis is the process by which a cell engulfs smaller organisms, food particles, or debris. This occurs when a cell's membrane extends outwards to surround and encase the material, forming a pocket that eventually fuses to create a vesicle within the cell. This is a common mechanism used by certain immune cells to ingest pathogens, allowing the body to defend itself against infections.

While exocytosis refers to the process of expelling materials from a cell, and hydrolysis involves breaking down compounds with the addition of water (a key process in digestion), neither of these terms describes the act of cell engulfing external substances. Autophagy, on the other hand, relates to the degradation and recycling of a cell’s own components rather than the ingestion of external material. Thus, phagocytosis is the specific term for the process described in the question.