The term 'rickety boat' is a phrase used to describe an old, dilapidated boat that is in need of repair. The crossword solution for this term is 'TUB', which is a three-letter word meaning a large, open container used for holding or storing liquids. This type of boat is often made of wood and is usually quite small, making it prone to wear and tear over time. As such, it is often referred to as a 'rickety boat'.