<p><strong>Noun</strong></p><ul><li>Physical Chemistry: a semirigid colloidal dispersion of a solid with a liquid or gas, as jelly, glue, etc.</li><li>Theater: gelatin (def 5).</li><li>Biochemistry: a semirigid polymer, as agarose, starch, cellulose acetate, or polyacrylamide, cast into slabs or cylinders for the electrophoretic separation of proteins and nucleic acids.</li></ul><p><strong>Verb (used without object)</strong></p><ul><li>gelled, gel·ling: to form or become a gel.</li><li>jell (def 2).</li></ul>