Pseudopodium is a temporary, protruding extension of a cell's cytoplasm used for movement and feeding, commonly found in amoeboid organisms. These extensions allow the cell to crawl along surfaces and engulf food particles through a process called phagocytosis. Pseudopodia can change shape and size, adapting to the cell's environment and needs. They play a crucial role in the locomotion and nutrient acquisition of certain single-celled organisms, such as amoebas.