Sack Flaps Share definition Flag Sack Flaps are a rare genital disease that gives the unlucky victim an extra, saggier pair of nuts. This extra pair usually hangs lower than the typical pair. Hey bro, do you have sack flaps!?? I could see them through your thin leggings. Sack Flaps by tambah May 1, 2024 Get the Sack Flaps mug.