The term 'rail at' means to vehemently criticize or rebuke someone or something. However, there are several synonyms that can be used to convey a similar meaning in different contexts. One such term is 'berate,' which means to scold or criticize harshly. Another synonym is 'lambaste,' which means to criticize severely or attack verbally. 'Castigate' is yet another similar term, meaning to criticize or reprimand severely. 'Denounce' can also be used to convey a similar meaning. In short, there are several synonyms available that can be used instead of 'rail at,' depending on the context and intent of the communication.