The phrase "connect up" can be replaced by many other synonyms depending on the context of the situation. Some alternative words that have similar meanings include link, join, attach, fasten, couple, bond, merge, unite, and tie together. These words are mostly used to describe the process of connecting two or more objects or ideas together. Additionally, the word "connect" itself can be used as a synonym for "connect up" and is often used in casual conversations. It is important to understand the different meanings of these synonymic words to properly communicate ideas and successfully accomplish tasks.