·noun High-sounding language, without importance or dignity of thought; boisterous, empty declamation; bombast; as, the rant of fanatics.
II. Rant·vi To rave in violent, high-sounding, or extravagant language, without dignity of thought; to be noisy, boisterous, and bombastic in talk or declamation; as, a ranting preacher.
rant
v.
1)(D; intr.) to rant at
2) (misc.) to rant and rave
Wikipedia
Diatribe
A diatribe (from the Greek διατριβή), also known less formally as rant, is a lengthy oration, though often reduced to writing, made in criticism of someone or something, often employing humor, sarcasm, and appeals to emotion.