flurgh

Flurgh is a non-comittal response given when you are uncertain as to what to reply to a question, or wish to obtain more information before answering. Usually used in reply to invitations to take part in sporting activities or social engagements.
On the whole flurgh leans toward being a negative answer, and is used when you don't want to give offense.

If you wish to be slightly more expansive on your meaning when using flurgh, the '+' and '-' signs may be used in conjunction with flurgh ie. maybe yes: +flurgh, and probably no: -flurgh.

Flurgh should never be spoken aloud, only ever written, but if it was pronounced it would sound phonetically almost exactly as it is spelled.