noun, noun or participle which takes 'suru', intransitive verb
verbal abuse; name-calling; abusive remarks
Dated reading and usage for harsh abusive language or insulting remarks. As a する noun it is old-fashioned; modern Japanese more often uses 悪口（わるぐち）, 罵倒, or ののしる depending on the nuance.
古い文章で「悪口する」とあれば、激しくののしることをいう。
In old writing, 悪口する read あっこうする means to abuse someone harshly.
その記録には、役人への悪口があったと記されている。
The record says that there were abusive remarks directed at the official.