Misconception: "Glatt Kosher" means something like "extra kosher" and applies to chicken and fish as well as meat.What?s the Truth About... Glatt Kosher
Fact: Glatt is Yiddish for smooth, and in the context of kashrut it means that the lungs of the animal were smooth, without any adhesions that could potentially prohibit the animal as a treifa, an issue only applicable to animals, not fowl or non-meat products.
Background: In colloquial discourse treif refers to anything that is not kosher. The technical definition of treifa is based on Exodus 22:30 ("Do not eat meat from an animal torn [treifa] in the field") and refers to an animal with any of a specific group of physical defects that are detailed in the Talmud (most of the third chapter of Chullin; 42a-59a) and codes (Rambam, Maachalot Asurot 4:6-9 and Shechitah ch. 5-11; Shulchan Aruch, YD 29-60). Examples of these "defects," which often go far beyond the health inspection of the USDA, include certain lesions, lacerations, broken limbs, missing or punctured organs, or the result of an attack by a larger animal. Such defects can occur in and thereby render both animals and fowl treif. Because most of these defects are uncommon, it may be assumed that most animals are healthy (Shach, YD 39:1) and hence there is no requirement to inspect every animal for them. An exception is the lung of an animal, on which adhesions [sirchot] and other problems may develop. While these problems are not common, they do occur more frequently than other treifot. Their relative prevalence led the rabbis to mandate that the lungs of every animal be examined, both manually while still in its natural position in the animal, and visually following its removal from the thoracic cavity (YD 39:1).2 Because a hole in the lung renders the animal a treifa, adhesions, i.e. pathologically arising bands of collagen fibers, are problematic either because they indicate the presence of a perforation that has been insufficiently sealed (Rashi) or because they can become loosened, thereby causing a hole to develop (Tosfot). In the U.S., lung adhesions usually do not occur on fowl; hence the rest of this discussion concerns only meat, not chicken.3»