A shiv, also known as a chiv, schiv, shivvie, or shank, is a handcrafted bladed weapon resembling a knife that is commonly associated with prison inmates). Since weapons are highly prohibited in the prison environment, the intended mode of concealment is central to a shivs construction. An especially thin handle, for instance, makes it easier to conceal in available cracks or crevices in the prisons construction, or in stacks of objects, such as books, permitted to the prisoners). Routine body searches in prison make it difficult to conceal a shiv on ones person on a continuous basis). The word shiv is recorded from the 1670s in the spelling chive as cant for knife, whose pronunciation is reflected in the spelling shiv recorded in underworld slang from 1915 and possibly used since the 1890s or earlier). The cant word probably came from the Romani word chiv for "blade"). The derived verb shiv means "to stab someone," and a shivver is an archaic or rarely used term for a criminal who attacks victims with a knife).

A shiv can be anything from a glass shard with fabric wrapped around one end to form a handle, to a razor blade stuck in the end of a toothbrush, to a simple toothbrush handle filed into a sharp point. The word shiv is slang for an improvised knife, and it generally applies to both stabbing and edged weapons. Shivs are usually made from available resources, such as toothbrushes, pieces of metal bunks, or sharpened spoons. The plural form of shiv is shivs.

In summary, a shiv is a makeshift bladed weapon resembling a knife that is commonly associated with prison inmates. It is usually made from contraband materials and is intended to be concealed due to the prohibition of weapons in the prison environment. The word shiv is slang for an improvised knife and generally applies to both stabbing and edged weapons.