"Suss out" is an informal expression that means to figure something out, usually through investigation or careful observation. This phrase is typically used in everyday conversation, but there are other synonyms for it that can be used in different contexts. Some of these synonyms include "decipher," "unravel," "uncover," "detect," "explore," "probe," "scrutinize," "analyze," "examine," and "investigate." These synonyms may be more appropriate in formal writing, specialized fields, or in situations where the intended meaning is more specific. It's important to understand the nuances of each of these synonyms to properly convey the intended meaning and tone.