Sussed is a British slang word used to describe someone who knows what is happening or who has figured something out. There are a variety of synonyms for sussed, including "clued up," "in the know," "savvy," "canny," and "aware." Other commonly used synonyms for sussed include "knowledgeable," "perceptive," "understanding," "well-informed," and "wise." These words are often used to describe someone who has a deep understanding of a particular subject or situation. Being sussed is essential for success in business or life, as having a thorough knowledge of a situation can help one make informed judgments and decisions.