The word itself decode its meaning that is kaal - "TIME" or sarp- "SNAKE" or serpent. Kaal Sarp dosh is very dangerous and inauspicious in anyone's chart. It shadows its bad effects on health, property and business. It makes the simplest work, the most difficult one.
Kaal Sarp Dosh occurs when all seven planets stuck between rahu and ketu. Rahu and Ketu are placed in front of each other in the chart. So, if all the planets rest between them, there is kaal sarp dosh. The time period for Kaal Sarp dosha is generally 47 years also it depends upon individual to individual.
There are twelve types of kaal sarp dosh according to the natal chart.