The phrase "slap in the face" is often used to describe an action or event that is insulting, humiliating or disrespectful. However, depending on the context, there are several synonyms that could convey varying levels of severity. For instance, a more mild synonym could be "snub," which suggests a sense of rejection but without the level of physical violence implied by a slap. "Insult," "offend," and "demean" are additional synonyms that convey a similar degree of offense without specifically implying physical harm. A more severe synonym could be "indignity" or "humiliation," which suggest a more significant insult to one's dignity or reputation. Ultimately, the choice of synonym depends on the nuances of the situation, and the level of severity of the offense.