The term 'untalkative sort' can be described as a 'CLAM, ' which is a four-letter word. A CLAM is a type of mollusk that lives in the ocean and is known for its ability to remain silent and still. Clams are usually found in shallow waters, where they feed on plankton and other small organisms. They are also known for their ability to close their shells tightly when disturbed, making them difficult to catch. As such, the term 'untalkative sort' is often used to describe someone who is quiet and reserved.