Materials that are "elastomeric" could also be said to be "elastic." Both terms describe what most people would refer to as "rubberiness," or behaving like rubber (which stretches and compresses, and returns to its original shape instantly after stress is removed).
The term given to a stretch yarn made chiefly from a filament of highly elastic polymer, such as polyurethane. Often elastomeric yarns can be covered with non-stretch fibres for greater control in weaving and knitting. The wrapping or covering is done by either core spinning or uptwisting. See elastic.