Blath"er, v.i. (imp. & p.p.) blathered; p. pr. & vb. n. blathering. Cf. Old Norse "bladhra." Also written blether.
To speak at some length in a foolish, nonsensical fashion; to utter gibberish.
Ex. In New York City, most people ignore the lunatics who stand on street corners blathering about their latest conspiracy theory.
Incoherent, nonsensical, foolish talk.
Ex. I wanted Professor Pedant to give me a clear, concise definition of existentialism, but instead he made me suffer through nearly an hour of blather