fill-in

noun

• A temporary replacement for another, especially at a job.
• A substitution.
• An intermediate result that must be stored temporarily during the course of a sparse matrix computation.
• A question or puzzle in which one is expected to fill in a missing part of something.
• A musical embellishment (usually percussion) that is added to connect musical phrases.
• Something added to fill a gap.
• Something added to increase the size of something; padding or filler.
• A product category that is used to complete a range or variety of a product line.