Geek, nerd, loser

My friends approached me about the difference between geek, nerd, and loser. While I think of loser as a universal term (as in, can be applied to any person with any characteristics, "smart" or not), I think of geeks and nerds on varying levels of intelligence (amongst other things), but I noticed that all of our opinions about the terms geek and nerd were different. What's the difference between the two? Smarts, grace in society, attitude? Are they semantically different, or do they mean the same? So how would you personally - without looking it up in whatever manner you look things up - describe the three terms?

And on a side note, which of the three terms would you apply to this description:
"Spends time reading intellectual books but isn't smart; awkward, and pretty much complete 'bumblefuck' around girls; doesn't get very good grades, but wants to get a PhD and generally does nothing of importance with his life - but acts like he does."



Edit: I didn't realize there was another post like this already. If someone links me to it, this one can be deleted/closed/what have you. There's too many posts in this community daily for it to be easy to keep up with the topics.