There are various synonyms for the word "break down." The first one is "deteriorate," meaning to gradually worsen or decay. Another synonym is "collapse," which suggests a sudden and dramatic failure. "Malfunction" and "fail" imply a technical problem or a system's inability to work as intended. "Crash" can mean a physical collision or a sudden stoppage, usually in reference to a vehicle. "Disintegrate," "splinter," and "shatter" indicate a total destruction or fragmentation. Lastly, "lose control" and "go berserk" refer to the loss of emotional or mental composure, usually accompanied by irrational behaviors or breakdowns.