The removal of an animal’s head, feet, hide and internal organs during processing. The carcase is now ready for further processing, which will be dependant on its market destination. 

Fish or game that has had guts (viscera) removed. In the case of fish, gills are removed, the cavity is cleaned, and the head and fins remain intact. The scales may or may not be removed.

A po'boy "dressed" contains lettuce, tomato, pickles, and mayonnaise or mustard.

(adj) dressed or clothed especially in fine attire; often used in combination(adj) treated with medications and protective covering(adj) (of lumber or stone) to trim and smooth(adj) dressed in fancy o [..]

Fish that has been gutted and had the entrails removed.

Whole fish that have been gutted, and scaled, and generally have also had their fins removed.

a po’boy served with mayonnaise, lettuce, tomatoes and pickles.

Dressed means “Prepared” for cooking. Item by item it can mean cleaned, dredged, breaded, stuffed, barded, larded, etc. Nutritional Value USDA

Sandwiches served with lettuce, tomatoes and mayonnaise: "the works" (and, of course...the way those with class catch their Mardi Gras throws!).

Sandwiches served with lettuce, tomatoes and mayonnaise-"the works"