Rood-tree is a word from Old English that refers to a tall, upright tree with a straight trunk. Although not commonly used today, there are several synonyms for this term. One alternative is the word "banner-staff," which describes a tall pole used to display flags or banners. Another term that can be used as a synonym for rood-tree is "staff-tree," which refers to a slender, straight tree that can be used as a walking stick. Additionally, the words "mast" or "pole" can be a substitute for rood-tree, especially when referring to the tall, straight trunk of a ship's mast or flagpole.