A macromolecule or oligomer molecule capable of entering, through reactive groups, into further polymerization, thereby contributing more than one monomeric unit to at least one chain of the final macromolecule. A pre-polymer molecule capable of entering into further polymerization through reactive end-groups, often deliberately introduced, is known as a telechelic molecule.
Source:
PAC, 1996, 68, 2287
(Glossary of basic terms in polymer science (IUPAC Recommendations 1996))
on page 2290