Heh....you may not be able to define 'bonk', but I'll be darned, when it happens you WILL know instantly.

I remember the first time I bonked it came out of nowhere...like 4 hours into a ride, I'm feeling strong and chipper, then suddenly, the bottom fell out from under me, just like that *snap~*

Whatever analogy you want to use....from falling in the mud, to someone taking the keys out of the ignition, to having your legs turn to wood - they all apply.

Veronica gives excellent advice - eat and keep a steady stream of calories coming - using whatever food combination works for you - digestion considered. Short of totally stuffing myself, ala several pizza slices etc - I find that I can handle most amounts of food and ride with no problem - actually ride better after having eaten than vice-versa.