Definitions for "onionskin"
A kind of thin but strong translucent paper with a glossy finish.
Lightweight paper. Basic size in 17" x 22"/500 sheets. Substance weights 7 to 10 lbs. Usually made from cotton fibers in qualities from 100% cotton fiber to 25%.
A translucent lightweight paper used for airmail stationery.
This option displays several (you decide how many) frames at once. The single frame highlighted in the timeline will remain solid, while the other frames appear somewhat transparent. Onionskin is useful for aligning and spacing graphics across multiple frames.