A teleseism is a tremor caused by an earthquake that is very far away. According to the USGS, the term teleseismic refers to earthquakes that occur more than 1000 km from the measurement site. Often teleseismic events can be picked up only by seismometers that are in low background noise locations; whereas, in general, a tremor of a magnitude 5.3 earthquake can be seen anywhere in the world with modern seismic instruments.
References
Teleseism Wikipedia(Text) CC BY-SA