centillion - a cardinal number represented in the U.S. by 1 followed by 303 zeros, and in Great Britain by 1 followed by 600 zeros.
This would lead to confusion if this number was ever actually used
ceratoid - hornlike; horny.
I can only imagine an English professor using this. "Honey, I'm feeling very ceratoid right now"
cerebrate - to use the mind; think or think about.
Dance to the music. Oh, yeah.
Cerenkov Radiation - radiation produced by a particle passing through a medium at a speed greater than that of light through the medium.
I guessed that this effect was impossible for a particle with mass to accomplish. I guessed wrong.