Word for someone who acts like an expert but who has very little knowledge?

What is a word to describe an individual who acts like an expert in a subject area, constantly stating facts and correcting people, but who actually has very little knowledge on the subject?

Solution 1:

Cryptonescient Morosophs and Ultracrepidarians

The cryptonescient are best described as morosophs and ultracrepidarians, as any philodox or sumpsimus drawn into this epeolatrous logomachy like a saturniïd to a pharol will deliciate in apprising you with all due impigrity.

Those epithets you may freely employ safe from all risk of nettling even the most inveterate of doryphores, for even if this should fail to deliver the recumbentibus you’re looking for, it should at least jargogle your nemetic opsimath long enough for you to avolate undetected under the supervenient obnubilation.

Solution 2:

Charlatan = a person who pretends or claims to have more knowledge or skill than he or she possesses; quack.

http://dictionary.reference.com/browse/charlatan

Solution 3:

This sounds like a poseur (M-W),

a person who pretends to be what he or she is not

In this case, posing as a knowledgeable person.