n. a person who pretends to become hyper or otherwise energized as a result of drinking coffee, despite not actually feeling any discernible effects, often to a ridiculously unnecessary degree.
etymology: portmanteau of caffeine and feign
That guy is such a caffeign! He's only skipping maniacally to the beat of Miley Cyrus because he expected to become energized by the coffee I gave him, but in reality I only gave him hot chocolate mixed with poop (i.e.: Starbucks cookies).