A spatial implosion is a type of spatial anomaly where space-time is compressed, crushing any objects occupying it.
A distortion ring that enveloped the USS Voyager in 2371 also seemed to act as a spatial implosion, that eventually would crush the ship. It later emerged that this was not the case, as the ring was in fact a lifeform that released Voyager unharmed. (VOY: "Twisted")