An exclamation intended to commemorate the occurence of a witty, jovially insulting, hilarously harsh or awkward comment, as well as lubricating the passage of conversation so as to facilitate further banter in the near future. It is most effectively used as a stand-alone catchphrase or vocal tool to break the awkward silence, indicate your approval of the previous comment or assert your position as the alpha banterer, or, in rarer circumstances, an effective "banter beacon", defined as one able to signal the presence of banter within moments of it appearing. Has been known to be used as a noun in the previously described ways but is certainly better employed as a single exclamation, leaving explanation of its context to those immediately adjacent to the utterer of the word. Has known to be used in conjunction with "Lad!" throughout history.
girl: "why do you keep throwing stones at me?"
boy: "probably because i don't ever wanna have sex with you"
banter beacon: "BAAAANTER!!!!"
mandem: "shu-hutt your mouth or im gonna stab you blud"
banter beacon: "i think that calls for...BAAAN-TERRR!
"*innocent comment by someone more socially vulnerable than you*"
"you have to start taking this more seriously or you'll mess it up for all of us"
head: "im afraid you're being expelled for what you did"
banterous individual: ".....im afraid you're being expelled for what i did"
head: "please, im trying to help you finish with your dignity intact"
banterous individual: "...that's what she said"
hidden banter beacon: "BAAAAAAANTER!"