The word "pa" can be used as an informal term for a father or dad. Some synonyms for "pa" include "papa," "pop," "daddy," "father," "old man," and "pops." These words are often used affectionately or casually when referring to one's father or someone who plays a father figure role in their life. Other words that can be used as synonyms for "pa" but have different connotations include "paternal," "progenitor," and "sire." It's important to choose the right synonym based on the context and tone of the situation to ensure clear communication.