Gibberish /ˈjib(ə)riSH / noun  

Definition: Gibberish describes meaningless speech, written words, and similar nonsense that most people don’t understand or take seriously. English speakers see someone speaking gibberish as unintelligent and nonsensical. 

People known for speaking gibberish are speaking in terms no one else can understand, and we often ignore them. The person speaking gibberish may or may not be aware that others can’t understand what they are saying. We often label any language, writing, or ideas we can’t understand as gibberish.

Etymology: The first recorded use of the word gibberish was in early 16th century English. Etymologists believe we derived the term from combining the words gibber and ish. The word gibber relates to excessive chatter and inarticulate speech. Ish is a Swedish term that denotes a language.

In a Sentence

I stopped listening to him when he began speaking gibberish.

The politician lost votes when his constituents found his campaign promises to be gibberish.

I can’t understand you when you’re speaking gibberish!

Synonyms 

Babble, Blather, Nonsense

Antonyms 

Logic, Meaningfulness, To The Point