When someone is deeply engaged in their thoughts, we often say that they are "immersed in thought." However, there are various synonyms that can be used to describe this state of mind. For instance, we can say that someone is "lost in thought," "absorbed in contemplation," "wrapped up in reflection," or "engrossed in ideas." Other synonyms for being absorbed in thought include "preoccupied," "rapt," "meditative," "pensive," and "contemplative." These words suggest different degrees and types of thoughtfulness, ranging from a gentle introspection to a profound concentration. Whatever the word choice, it is clear that when someone is immersed in thought, they are fully caught up in the workings of their own mind.