Cytoplasm is the cell's gel-like interior containing organelles, supporting structures, and facilitating essential cellular functions, excluding the nucleus. The cytoplasm is briefly discussed here. CYTOPLASM definition: 1. the substance inside a cell that surrounds the cell's nucleus 2. the substance inside a cell…. Learn more. Cytoplasm is the fluid that fills the cell and contains various components such as cytosol, organelles, proteins and ions. Learn about the structure, function and properties of cytoplasm , and how it differs between eukaryotic and prokaryotic cells. Cytoplasm is a semi-fluid, gel-like substance found in all living cells, both prokaryotic and eukaryotic. It surrounds the cell's organelles and nucleus. It acts as the medium in which various cellular processes like protein synthesis, metabolism, and many chemical reactions take place.