When we talk about covering up for someone, we refer to the act of protecting them from negative consequences or hiding their wrongdoings. There are many different ways to express this idea using synonyms. One option is to use the phrase "give an alibi for," which means providing a false explanation to prevent someone from getting in trouble. Another synonym is "conceal," which means hiding something or keeping it secret. "Protect," "shield," and "defend" are other synonyms that capture the idea of guarding someone from harm. No matter which synonym you choose, cover up for someone always involves a level of dishonesty or deception.