A spherical, osmotically-sensitive cell without its cell wall but retaining an intact cell membrane. Protoplasts are used to create hybrid cells via protoplast fusion.
Source:
PAC, 1992, 64, 143. 'Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)' on page 164 (https://doi.org/10.1351/pac199264010143)