The expression "be in the land of Nod" refers to being asleep or in a deep sleep. There are several synonyms for this phrase, including being "in the arms of Morpheus," which is a reference to the Greek mythological god of sleep. Other synonyms include being "in dreamland," "in slumberland," and "catching some z's." These phrases all convey the idea of being in a state of deep sleep, where one is completely unaware of their surroundings. Other synonyms for "be in the land of Nod" may vary depending on the region and the dialect being used.