Name the material first
Laboratory-grown diamond is diamond produced in a controlled environment. In gemmological use, synthetic can describe a laboratory-created counterpart of a natural material. It does not simply mean an imitation.
Keep lookalikes separate
Moissanite and cubic zirconia are distinct materials. A seller should not use an ambiguous description to conceal that difference. Look for the exact material, origin and supporting report information in the written offer.
Sources and further reading
This English edition draws on the source material referenced below.