booklouse Syllabification: (book·louse)Pronunciation: /ˈbo͝okˌlous/Definition of booklouse noun (plural booklice) a minute insect that typically has reduced or absent wings and often lives in books or papers, where it feeds on mold. Liposcelidae and related families in the order Psocoptera: many species booklouse in other Oxford dictionaries Definition of booklouse in the British & World English dictionary