To understand what "SHUD" means, it's important to have more context.
Please provide more information, such as:
* Where did you encounter this term? (e.g., a salon, a hairdressing website, a conversation with a stylist)
* What was the context of the term? (e.g., was it in a product description, a technique explanation, a stylist's instruction)
With more details, I can help you figure out the meaning of "SHUD" in this specific instance.