"Down pat" is a common idiom that refers to the state of having something mastered and completely under control. While there are a few lesser-known synonyms for this phrase, some of the most popular and widely used include "down cold," "down solid," and "down to a science." All of these alternatives convey the same meaning as "down pat" and are often used interchangeably depending on the situation. Other possible synonyms that may be used less frequently include "down locked" or "down tight." However, regardless of which phrase is used, the message is clear that someone has thoroughly mastered their task or skill.