What is "brain fag"

Cerebropathy \Cer`e*brop"a*thy\, n. [Cerebrum + Gr. ? suffering.] (Med.) A hypochondriacal condition verging upon insanity, occurring in those whose brains have been unduly taxed; -- called also brain fag.

n. 1 A condition to which male high school and college students are prone consisting of difficulty in concentrating, mild forgetfulness, and difficulty in maintaining a train of thought, arising from "too much thinking". Physical symptoms can manifest as well. 2 cerebropathy