A Silkwood shower is a very long, hot shower taken to disinfect and decontaminate oneself from environmentally acquired smells such as smoke or food.
The term stems from the name Karen Silkwood. She was a chemical technician who died under mysterious circumstances after raising issues of contamination at the plant where she worked.
In 1983 a movie named Silkwood was released which starred Meryl Streep, Kurt Russell, and Cher. There is a decontamination shower scene in that film which is the basis for the term being coined.
I had to take a Silkwood shower when I got home from that party since I smelled like an ash tray cooked on a open flame BBQ grill covered in hot sauce.