Rudrabhishekam is worship of Shiva in his Rudra Form.

Rudrabhishekam is worship of Shiva in his Rudra Form. It is hailed by all Vedic scriptures. Lord Rama performed Rudrabhishekam at Rameshwaram to seek blessings of Shiva and for atonement of sins. This abhishekam is performed to wash away one's sin and bring home prosperity and happiness in the family. Pradosham is the one of the favourite days for Shiva and this Rudrabhishekam can be performed on this day. Or alternatively Monday's is also considered to be auspicious day for Lord Shiva. It is performed in this month of Savan also. Rudrabhishekam to be accompanied by the recital of Namakam and Chamakam. ‪Shri Rudram is the basis of Yajurveda, with the sacred Siva Panchakshari Mantra enshrined in it. Rudram dedicated to His worship is regarded as the removal of all sins and the giver of all that one desires. It is recited while performing Rudrabhishekam. His Maha Mrityunjaya Mantra can also be chanted, which is the best remedy for health problems. Rudrabhishekam is the worship of Shivlingam by bathing him with the prescribed ingredients such as honey, curd, ghee and milk with chants on the Sri Rudram. The puja wipes out all sins and purifies the atmosphere. It also removes all sorts of planetary doshams. Constant repetition of Shri Rudram in the prescribed manner is done. It is chanted eleven times. It is followed by Abhishek ,Hawan and Archana to Lord Shiva. During Rudrabhiskeham, the following offerings are made to Lord Shiva ~ Milk, Buttermilk, Yoghurt, Honey, Sugar, Juice, Ashes or Bhasam, sandlewood, Oil. While offering these, Sri Rudram is chanted along with 108 names of Lord Shiva and many more shlokas that help us get into favour with Lord Shiva. Fruit, flowers, bilva leaves, rudraksha, incense, coconut etc. also offered to Shiva.
Om Namah Shivaya !