Define Going Off On One Meaning

Going Off On One
Idiom (UK), see go off on one. To launch into a rant or lengthy discussion about some pet subject.

Might be derived from "going off on a tangent", but has more of a connotation of annoyance.

Sorry for going off on one, but I really feel strongly about this.
By Conny
Go Off On One
To be provoked by someone/something to such a point that a verbal reaction becomes inevitable.

Why's that kid shitting on Tom's car? Tom's gonna go off on one in a minute.
By Gwenni