noun

• (pathology) A large vesicle or bulla, usually containing a serous fluid.
  "2008, Lin Her-Shyuan Lin, Adam C, Reynolds, 180: Filtering Blebs and Associated Problems, Frederick Hampton Roy, Frederick W. Fraunfelder, Frederick T. Fraunfelder (editors), Roy and Fraunfelder's Current Ocular Therapy, 6th Edition, page 340, Inflammation and scarring is a shared mechanism for chemical irritants, cryotherapy, laser thermotherapy, and autologous blood injection in the treatment of bleb dysesthesia, overfiltering blebs, and bleb leaks."
• (cytology) An irregular bulge in the plasma membrane of a cell undergoing apoptosis.
  "Figure 4.20 reveals blebs on the surface of a bacterial cell. In many instances, these blebs are released from the cell into the surrounding media."
• (geology) A bubble-like inclusion of one mineral within another.
  "1974, George E. Stoertz, George E. Ericksen, Geology of Salars in Northern Chile, Geological Survey Professional Paper 811, page 32, Figure 23. […] The crust is underlain by silty sand, which is loosely cemented by a meshwork of gypsum crystals and contains blebs and small nodules of white ulexite (U)."