An adjective combination of 'girlfriend' and 'less'. A term used to describe when a person (usually a male) is lacking a girlfriend. I.e 'girlfriendless'. Usually a common affliction in nerds and young adolescent boys.
Can also be modified slightly to describe a state or condition of 'girlfriendlessness'. This is a common condition found on WoW forums.
Another variation is 'girlfriendlessly' used to describe one-wordedly the condition of being girlfriendless.
Mother: 'hey, haven't you found a girl yet?'
Son: '(sigh) nope, I'm currently girlfriendless'
Cute Girl: 'Hey aren't you together with (insert name here)?'
Boy: 'Nope, I'm girlfriendless and totally free'
Person A: 'I can feel the girlfriendlessness on this forum dude'
Person B: 'Yea this is a blatant sausage fest'
Person 1: 'OMG look at Roger! He is girlfriendlessly driven for poon tang today!'
Person 2: 'Yea, he is even hitting on the butter-faces... he must have blue balls. His girlfriendlessness is getting on my nerves.'
Roger (to girl): 'Listen, I've been so girlfriendless for so long right now just a whiff of your perfume is making me pitch a tent'