INTRANSIT means that a book belonging to one USC library was returned to another USC library and is now in the process of being returned to its home library.
This process can take anywhere between two to three business days. Sometimes--especially at the end of the semester--it can take a little longer because of the large number of books being returned.
Sometimes, the book has returned to the home library but the record has not been properly updated. You may want to contact the circulation staff at the home library to confirm that the book is not in the bookstacks.
[Screenshot of search result that identifies a book as "intransit"]