U 

Unauthorized

 written without the subject's cooperation or consent.

Unbound

 Refers to a book which has never been bound. Until the 19th century, books were sold as unbound leaves that were bound to a buyer's specifications. This term might also refer to a book in an advanced state of publication, such as a galley.

Uncorrected Proof

 See proofs.

Uncut

 Refers to the untrimmed pages of a book—the edges appear rough and uneven. In early bookbinding, the unbound pages of a book were left uncut until the binder trimmed them flush and smooth as part of the binding process. Today the terms uncut and unopened are often used synonymously. See also deckle edges.

Underlining

 The pen or pencil markings where the previous owner marked the book to highlight words, sentences, and/or passages of text.

Underrun

 To receive fewer books than ordered. This may occur because of spoilage during printing or printer's error.

Unopened

 The folded edges of the signatures have not been cut open for reading. The book has been left in the beginning stages of its binding process or it was issued in this manner.

Unpaginated (Unpag)

 The pages of the publication are unnumbered.

Unsophisticated

 Refers to condition; the book is fairly worn and has not been repaired. It can also refer to an incomplete manuscript that has been completed by using a different source or by someone besides the author. Unsophisticated can also refer to a book or pamphlet that is manufactured in an amateurish manner.