A shack is a type of small house that is in disrepair. The word may derive from the Nahuatl (Aztec) word xacalli or "adobe house" by way of Mexican Spanish xacal/jacal, which has the same meaning as "shack" It was a common usage among people of Mexican ancestry throughout the U.S. southwest and was picked up by speakers of American English.
In Australia, particularly in Tasmania, shacks were originally holiday homes located on crown land such as along river banks (especially the Murray River) or near beaches. They were roughly built as they were likely to get washed away in floods, and had no legal title on the land they were built on. Now, a lot of the shack owners have freehold title to their land, and are subject to building codes to reduce the risk of damage or injury from floods and storms. Many are now quite grand holiday homes and summer houses. The New Zealand equivalent is called a bach.
In South Africa, shacks (also referred to as mikhukhu or imijondolo ) are an increasingly common form of accommodation for millions of people and are mostly found in or around urban areas, particularly on the outskirts of larger cities. In recent years shack dwellers have organised major protests around the country. The largest movement of shack dwellers is called Abahlali baseMjondolo (loosely translated: "The Residents from the Shacks").