A professional trainer or savvy bike shop employee can fit your bike to you by adjusting the height of the seat, position of the handlebars, angle of your pedlas, etc. For athletes this means more powerful pedaling. For commuters this can mean more comfortable riding. If you experience back, shoulder or neck pain, consider getting a bike fit.
In the biking world, "clipless" means that your shoes DO clip in to the pedals, like a little ski binding almost. You could call them "clip-in" or "cleated" too. Eventually, you should give it a try. Most people get used to it after a few rides and the rewards are awesome: more power, more efficient, faster up hills.
A cycling sport that takes place in the fall and winter, where confused cyclists put knobby tires on their road bikes and race them on relatively smooth off-road paths. The sport is characterized by the rider's often dismounting their steads to run up a short hill or jump over obstacles such a short fences. Cyclocross is often "enjoyed" in the snow, rain and mud. This sport has a long and interesting history. More info at Wikipedia.
When the door of a parked car is opened in front of you and you hit it, you have been doored. This exciting activity is often followed by being run over. Try to stay out of the way of doors that might open.
A bicycle that makes pedaling easier by assisting the rider with an electric motor while the pedals are being turned.
A floor pump is a "stand up" tire pump that you keep in the garage, as opposed to a small portable pump that you might carry on your bike. Floor pumps are essential for anyone who bikes a lot. They inflate a tire much faster and easier than a portable pump. It is hard to reach the pressure you need with a portable pump, and it is easy to break the valve stem off your tube. Keep a portable pump in your pack, but keep a floor pump at home.
An electric bike that is powered entirely by an electric motor, no pedaling. I'd argue that this is a scooter, not a bicycle.
A snot rocket is acheived by closing one nostril with a finger and forcibly expelling snot out of the other. Such measures are typical on autumn and winter days when the wind chill causes a runny nose. It is common courtesy to make sure that no one is behind you before expelling snot in this manner. There is possibly nothing worse than having someone else's snot land on your face.