Definition: In table tennis, tensor rubber is the common name used by players for any table tennis rubber that has the topsheet stretched and placed under tension before it is glued to the sponge. This tension tends to cause the rubber to curl inwards with the sponge on the outside, doming the rubber sheet.
In order to attach the rubber to the blade, the rubber must be flattened, which places the topsheet back under tension, and increases the catapult effect which can be obtained from the rubber.