Protoplasts are plant cells without cell walls. When it comes to synonyms for protoplasts, there are several related terms. One synonym is "naked cells," which refers to the lack of a cell wall. Another term is "plasmolyzed cells," which refers to the process of shrinking the cell contents by removing water. "De-walled cells" or "wall-less cells" can also be used to describe protoplasts. Additionally, the term "spheroplasts" can be used to describe protoplasts in bacterial cells, which refers to the spherical shape of the cell membrane-bound structure resulting from the removal of the cell wall. Overall, these terms are used interchangeably to describe the same concept of cells without a cell wall.