The<unk>  refers to a large oval radiolucency in the shape of an American<unk> , which is seen on supine abdominal X-ray films. The<unk>  is most frequently seen in infants with spontaneous or iatrogenic gastric perforation causing pneumoperitoneum.
Football sign
Lincoln sign
Quincke sign
Steeple sign
Puddle sign
Westermark sign
Mayen sign
Lighthouse sign