Glycoproteins isolated from plants but recently found also in animals and microorganisms that react specifically with terminal glycosidic residues of other molecules (e.g. cell wall polysaccharides); some causing cells to agglutinate (cf. agglutination).
Source:
PAC, 1992, 64, 143. 'Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)' on page 158 (https://doi.org/10.1351/pac199264010143)