Jibber-jabber can be thought of as speech made with the rapidity engendered by panic or anxiety. Its subject may seem confusing and non-linear.
As noted by that great philosopher Mr. T, who was oft found to wax dismissive with his remark, "I ain't got time for your jibber-jabber!", this class of speech can best be described as specious - it appears to have rational sense on its surface, but underneath it is often found to be complete bollocks, and bereft of any real meaning or application, other than that within its closed-world.
Whilst many synonyms may exist - such as horseshit - one must not mistake 'jibber-jabber' for being something akin to 'mendacity'. Whereas the latter implies a willful deception, the use of jibber-jabber is often due to lack of knowledge by the speaker, or a desire to impress the listener.
In many respects, the guidelines in the second definition that determine what is patent nonsense may also be applied here, albeit to a limited extent.
Wikipedia may often appear to contain a pullulation of examples of jibber-jabber. But closer examination may also reveal that, in fact, such an appellation points towards lack of specialist knowledge on the part of the one making such a judgment. Hence, jibber-jabber may appear as such from ignorance rather than fact.