Theresa-ing Share definition Flag The act of using writing utencils improperly, or all around goofing off in science class. When Tess took my highlighter and started drawing randomly, she was theresa-ing. Theresa-ing by theresawastheresaing February 27, 2011 0 0 Get merch Get the Theresa-ing mug. Buy Now — $32.95 See more merch