There are several synonyms available for the phrase "make fast." The phrase can mean to secure or attach something firmly in place. In this context, synonyms could include fasten, attach, fix, secure, or tighten. Alternatively, "make fast" could mean to quicken something's pace or speed. In this sense, synonyms could include accelerate, hasten, hurry, or speed up. Finally, "make fast" could mean to secure or tie up an object or vessel, such as a boat. Synonyms in this context may include moor, berth, dock, or tie up. Depending on the context, there are many options available to choose from when searching for synonyms for the phrase "make fast".