In chemistry, an oligomer consists of a limited number of monomer units, in contrast to a polymer which, at least in principle, consists of an unbounded number of monomers. Many oils are oligomeric, such as liquid paraffin. Plasticizers are oligomeric esters widely used to soften thermoplastics such as PVC. They may be made from monomers by linking them together, or by separation from the higher fractions of crude oil. Polybutene is an oligomeric oil used to make putty.
Source: Wikipedia