Erudite
Knowledgeable, Scholarly
Esoteric
Specialized knowledge, only understood by a select few
Exacerbate
To make worse
Exculpate
To clear from blame, to prove not guilty
Extant
Still in existence
Extraneous
Extra, unnecessary
Feckless
Lacking purpose, careless/irresponsible
Feign
To pretend
Fractious
Difficult to control, irritable
Hubris
Excessive pride