When people are talking all around you, yet you are off in your own little world. No friends. When nobody pays attention to you. Loser. Lost.

The present tense verb for doing something on your own, especially when friends of yours are available and you are inexplicably just trying to appear cooler than them. Also often applied to people who you want to point out are boring loners.

A feeling that is indescribable to those who have not felt it, and needs no description to those who have. That desolate feeling of being left out, left behind, and being all alone forever. This not only applies to girlfriends(though they bring the strongest effect) but also major life changes - graduation, deaths, etc... It is that hole that appears in your heart, which cannot be filled by your efforts alone. In such a case, crying occurs and is often encouraged as it heals the soul.

Adjective
1. An adjective describing one who finds him or her self looking up words such as lonely on urbandictionary.com because he or she misses his or her loved one, or has not yet found one to be named as such.

-or-

2. 12:42 a.m.: Sitting in front of a computer in the dead of night, wondering where the girl that you've fallen madly in love with is and most of all, why she's not here, next to you. Usually this condition can be cured by random yet enthusiastic reiteration of the phrase: "I love you, Diana!"

A powerful feeling of emptiness and isolation; feeling disconnected and alienated from other people.

One of the saddest feelings possible. It can be from not having a partner, not having friends, or not having either. A lonely person can be very sad, and won't have anyone to comfort them. It can be hard to break out of loneliness. Some people are lonely for years at a time, or maybe just one night.

Unloved. Unhappy. In pain, not just mental but physical too.