The process of converting a monomer or a mixture of monomers into an oligomer. An oligomerization by chain reaction carried out in the presence of a large amount of chain-transfer agent, so that the end-groups are essentially fragments of the chain-transfer agent, is termed telomerization.
PAC, 1996, 68, 2287. 'Glossary of basic terms in polymer science (IUPAC Recommendations 1996)' on page 2306 (https://doi.org/10.1351/pac199668122287)