What does he mean by needing a girlfriend?

Usually when a guy says that, it means that, he needs a girlfriend. He's lonely, he needs someone by his side, it's sorta like an emotional support to know that someone loves you, cares about you, and is by your side. It's different than parents' love, you know? Besides, he probably has seen others with girlfriends and is now wanting the sort of feeling associated having a girl next to you whom you can kiss/cuddle with, etc etc. It's different to have a girlfriend and to be alone, it feels better for some guys to have girls.

It means a man wants a woman to give a damn about other than just for sex. Otherwise he would have said, "I need to get laid". If this is going to be a long-distance relationship, you better drop the bomb on him as these almost never work out at all. Of course, distance is relative but if meeting is going to be rare in frequency say, twice a year. Forget it.

Believe me, men want to be with women more so than vice versa. NEVER EVER EVER underestimate the power of loneliness, it can and will make people do some desperate things equal in determination and results as addiction, jealousy and hate. The difference is that loneliness can be cured willingly for positive results. Those who hate, need a drug hit or seek jealous revenge are lost.

If you ask me, this guy is feeling horny as everybody else has said.

Overall, it would be cool to introduce your friend to a down to earth descent girl.

It means exactly what he said, he wants someone to love, hold, cherish, and have healthy sex with - in short, a mate. If he just wanted sex, there's tons of skanks and fat chicks out there.

Well I realize that you asked for a guy to answer this, but I feel like I have a valid opinion. I have had multiple friends that are guys. In fact, my best friend is a guy. When you ask yourself this question think about. "What does it mean when an 18 year old girl says to the person (guy) they confide in, I really need a boyfriend? " honestly, it all depends on the social context. Was he saying it in a joking manner or did he seem completely serious. My guess is, especially at an older age, that he was serious. I am not sure of your relationship status, but what I do know is that at a certain age people begn to feel lonely, even though they have great friends and family support. There is a certain intimacy, compassion, and committment that is involved in a "good" (ideal) relationship. This is more than able to be observed by people. And face it, we are socialized to want to fall in love some day and create that ideal life. Men & Woman are REALLY not that different. So next time you ask think of what a man is thinking or meaning by a comment. Think of it by the true honest woman. We need not to lie to ourselves about our thoughts, emotions, or impulses and society pressures.
So why is he saying he "needs" a girlfriend.? Because he feels like he does. Whether it be for intimacy, committment, compassion or all three, Men & Women are all social animals that have needs and presses that drive our emotions, even though we don't always express it.

Horny? I doubt it, unless there are more indicators. Maybe he's trying to hint around, at you or a friend of yours, or maybe it's simple - he wants to find a girlfriend. You never know.