What does bleb mean?
A bleb is a small blister or bubble — a localized swelling filled with fluid or air that forms on the skin, on a membrane, or on the surface of a material. The word appears most frequently in medical and scientific writing. Dermatologists use it for blister-like skin lesions, ophthalmologists for the raised pockets that form after glaucoma filtering surgery, and cell biologists for the rounded protrusions that emerge from a cell's membrane as it undergoes apoptosis, or programmed death. Outside technical use, a bleb can simply be a tiny bubble trapped beneath paint, glass, or another surface. The word carries no emotional connotation; it is neutral, precise, and largely confined to professional registers. Its diminutive, slightly whimsical sound belies its usefulness: few other English words so neatly capture the idea of a miniature blister, making 'bleb' a valuable term for anyone reading medical literature or describing fine-grained surface defects.
A small blister or bubble, especially one filled with fluid, forming on skin or on a surface.
"A tiny bleb rose where the mosquito had bitten him."
In medical usage, distinguished from larger blisters (bullae) by size.
In cell biology, a rounded protrusion of the plasma membrane, characteristic of cells undergoing apoptosis.
"Fluorescence microscopy revealed numerous blebs budding from the apoptotic cell."
Standard regular plural; used freely in both clinical and laboratory contexts.
"The biopsy showed multiple blebs scattered across the tissue sample."
Your own cells make blebs every day — when a cell undergoes apoptosis, it literally bubbles apart into membrane blebs before being tidily consumed.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bleb
The word 'bleb' first appears in English in the early seventeenth century, though its ultimate origin is uncertain; lexicographers have suggested it may be an expressive or imitative formation, possibly related to words like 'blob'. It has long served as a small-scale counterpart to 'blister' and 'bubble', and its adoption by pathology and later cell biology gave it a stable technical footing.
Related word forms
How bleb is actually used
Most common in medical, pathological, and cell-biological contexts; rare in everyday speech. In medicine, 'bleb' often refers to a raised blister-like lesion, such as those seen in bullous pemphigoid or after certain surgical procedures (e.g., filtration blebs after glaucoma surgery).
Easily confused with bleb
A 'blob' is any soft, shapeless mass, while a 'bleb' is specifically a small blister-like bubble or swelling.