A rant is an argument that is fueled by passion, not shaped by facts. When the shouting starts on talk radio, or when a blog commenter resorts to ALL CAPS — you're almost certainly encountering an instance of ranting.

Rant comes from the Dutch ranten, "to talk nonsense." Rave is a close synonym — in fact, "to rant and rave" is a popular expression. When rant is used as a noun, it means something like tirade. The first recorded usage of rant is from the end of the sixteenth century, in Shakespeare's The Merry Wives of Windsor. By the middle of the turbulent seventeenth century, the name Ranters was used as a catchall pejorative for various groups of radical Christian dissenters.

Definitions of rant

v talk in a noisy, excited, or declamatory manner

jabber, mouth off, rabbit on, rave, spout
Type of:
mouth, speak, talk, utter, verbalise, verbalize
express in speech

n a loud bombastic declamation expressed with strong emotion

harangue, ranting
a long monotonous harangue
Type of:
vehement oratory

n pompous or pretentious talk or writing

blah, bombast, claptrap, fustian
Type of:
grandiloquence, grandiosity, magniloquence, ornateness, rhetoric
high-flown style; excessive use of verbal ornamentation