1) A vacuole is a membrane-bound cell organelle. In animal cells, vacuoles are generally small and help sequester waste products. In plant cells, vacuoles help maintain water balance. Sometimes a single vacuole can take up most of the interior space of the plant cell.

2) A small cavity or space in the tissues of an organism containing air or fluid.

3) A cavity or vesicle in the cytoplasm of a cell containing fluid.