1) Jack jabbered away about his job all day.
2) Jack rambled on about his job all day.
3) When he chairs the meeting he always jabbers away.
4) When he chairs the meeting he always rambles on.
According to you, do these two verbs mean to speak at length, without going to the point?
Would you use them both? How does a native speaker use them correctly in everyday's English?
I'd use jabber when someone speaks nervously and doesn't make much sense, while rambling is talking at length, often with digressions.