A welt can refer to different things depending on the context. Here are some definitions:

• Shoe-making: A strip of material, usually leather, between a shoe sole and upper through which they are stitched or stapled together.
• Medical: A red bump, ridge, or swelling of unbroken skin raised by a stinging blow or by an allergic reaction to foods, drugs, or insect bites, as in hives.
• General: A ridge or wale on the surface of the body, as from a blow of a stick or whip.
• Sewing: A strip of fabric used to cover or bind one or both edges of a pocket opening.

In summary, a welt can refer to a strip of material used in shoe-making, a raised bump on the skin, a ridge on the surface of the body, or a strip of fabric used in sewing.