Those people who can't adjust to the regular standards of society;
Often seen as awkward in a social sense;
Introverted - most are introverted and I think it's because of the socially awkward thing;
Often seek refuge in virtual realities that make them feel more important perhaps, like video games, taking on other identities, becoming engulfed in fantasy / sci fi things - subjects that allow the individual to alter realism into a way where they become special, unique, gifted, or spectacular in someway - I'm guessing to make up for the lack of being in true time.
Some are annoying - some are incredibly hilarious - some are kinda mean or bitter -
They're all pretty cool if you actually take the chance to get to know them, and not avoid them like so many people tend to do, or judge them.
I'd probably think of a geek/nerd as someone who is pretty intelligent, usually seen as socially awkward and shy, obsesses themselves with computers, math, science or even WoW and knows Pi as 3.14159265. ;)
I would say I'm a nerd in someways.. nerds can be pretty cute too.
Yagurlnira768's answer is right on - I think, anyways.
A geek or nerd is someone who is very smart - studies, does very well on exams and quizzes and has the most intricate and complex ways of doing things. Some can be awkward but if you think about it, they can be better later in life.
someone who will give you false hope and smash your heart into little pieces...
I'm married to a guy who considers himself a nerd, as in he just plays video games and likes computers.
I think that's fine, those hobbies go with me because I just like to sit all day and do nothing (some times play puzzle fighters and mario wii other times nothing) and so we match.
Plus nerds are really smart, and they have 4.0s and can past college courses with blind colors so therefore they will be banking some day! :) at least I know my guy is going to be... because he's so smart he already is (he's into computer networking, routers and switches)