#Lightweight Offset Paper Regular folks outside the printing industry normally call this Bible paper or sometimes rice paper, but the technical term used by the printing industry for this lightweight offset paper.
From Wikipedia:
Bible paper is a thin grade of paper used for printing books which have a large number of pages. Technically it is called lightweight offset paper and is a type of woodfree uncoated paper. This paper grade often contains cotton or linen fibres to increase its strength in spite of its thinness.