Polyethylene glycol (PEG)-conjugated proteins belong to a new class of biomolecules that are neither proteins nor polymers, but which are hybrids of the two. PEG conjugation of biopharmaceuticals is now common practice in efforts to achieve sustained clinical response. Glycerin definition is - glycerol. Recent Examples on the Web For dry skin on the face, choose a formula that also contains moisturizing ingredients, such as glycerin. ... Definition of PEGylation in the Definitions.net dictionary. Meaning of PEGylation. What does PEGylation mean? Information and translations of PEGylation in the most comprehensive dictionary definitions resource on the web.