The phrase "have a stab" is synonymous with "make an attempt" or "take a shot." However, there are several antonyms for this phrase depending on the context. Some of the antonyms of "have a stab" are "give up," "quit," and "abandon." These words suggest a lack of confidence, determination, or belief in oneself to complete a task. Other antonyms for "have a stab" include "refrain," "abstain," and "avoid." These words signal a conscious decision to not participate or engage in a particular activity. So, depending on the situation, using an antonym for "have a stab" can provide clarity and nuance to a sentence.