What is a 'thneed' in the Lorax?

In Dr. Seuss's book "The Lorax," a "thneed" is a versatile object that can serve multiple purposes, such as a garment or a blanket. The concept of the thneed symbolizes consumerism and the destruction of the environment for profit in the story. The Once-ler creates the thneed from the tufts of the Truffula trees, leading to the devastation of the forest and the extinction of the creatures that depend on it.