Daydreamer is a common word used to describe someone who is lost in thoughts and has a tendency to imagine things. However, there are several other synonyms for "daydreamer" that can be used interchangeably. One might use the word "fantasizer" to describe someone who is constantly lost in their dreams and fantasies. Similarly, the words "dreamer" and "imaginist" can be used to describe someone who has an imaginative mind and keeps getting lost in their own thoughts. Other synonyms include "muser," "romantic," "wanderer," "idealist," and "visionary." Whichever synonym is used, it describes someone who likes to think ahead and picture of a future that's more exciting than the present.