An arabesque, also known as the "line of continuity," collects, organizes, and relates different elements in a composition. An arabesque can be used to tie in the background with the foreground or connect specific components together in a design to create a sense of unity. A well-designed arabesque will allow the viewer's eyes to move fluidly (without hesitation) through a composition in a drawing, painting, or photograph. The example below, from the Myron Barnstone drawing DVD series, demonstrates the arabesque in a Francisco Zúñiga drawing.
Additional Examples of the Arabesque in Composition
Image above, “Birth of Venus” by Botticelli, demonstrating the use of the arabesque
Image above, “The Rape of Europa” by Paolo Veronese, demonstrating the use of the arabesque
Image above by George Frederic Watts demonstrating the arabesque in a composition. Notice how the arabesque is complemented by the strong use of straight and diagonal lines. To learn more about the use of lines in a work of art, I recommend chapter three of the book Classical Drawing Atelier by Juliette Aristides.