filler

:  one that fills: as a :  a substance added to a product (as to increase bulk, weight, viscosity, opacity, or strength) b :  a composition used to fill the pores and grain especially of a wood surface before painting or varnishing c :  a piece used to cover or fill in a space between two parts of a structure d :  tobacco used to form the core of a cigar e :  material used to fill extra space in a column or page of a newspaper or magazine or to increase the size of a work (as a book) f :  a pack of paper for a loose-leaf notebook g :  a sound, word, or phrase (as “you know?”) used to fill pauses in speaking