Sub tending refers to the act of extending under or supporting something. There are several synonyms for this word, including undergirding, sustaining, maintaining, upholding, buttressing and reinforcing. Each of these synonyms conveys the idea of providing support or foundation for something, be it an idea, concept, structure, or object. For example, in architecture, a building's foundation is crucial in sub tending the entire structure's weight and ensuring it remains stable. Similarly, in debate or argument, a well-supported argument can be considered as sub tending your viewpoint. In summary, the synonyms for sub tending all convey the idea of providing support and usefulness to something or someone.