Backing can refer to different things depending on the context. Here are some definitions of backing from the search results:

• Support or endorsement: Backing can refer to support, especially financial support, that someone gives to a person or plan. It can also refer to endorsement, especially of a warrant by a magistrate.

• Musical accompaniment: Backing can refer to the music that is played along with someone who is singing or playing the main tune. It is the music that accompanies the lead musician.

• Phonological process: Backing can refer to a substitutive process in speech therapy that involves articulating the sounds produced in the front of the mouth, such as T and D, in the back of the mouth instead. This process is generally considered to be indicative of a more severe phonological delay.

• Supporting argument: In the Toulmin model of argument, backing is the support or explanation provided for the warrant. It is often characterized by the word "because" and provides additional evidence or reasoning to support the claim.

• Something that supports or strengthens: Backing can refer to something that forms the back or is placed at or attached to the back of anything to support, strengthen, or protect it. For example, a tape with adhesive backing has a layer of adhesive on one side and a backing material on the other side.

In summary, backing can refer to support or endorsement, musical accompaniment, a phonological process in speech therapy, a supporting argument, or something that supports or strengthens.