neck·beard
/ˈnekbird/
noun informal
noun: neckbeard; plural noun: neckbeards; noun: neck beard; plural noun: neck beards

a growth of hair on a man's neck, especially when regarded as indicative of poor grooming.
"I can picture myself wearing these clothes a week from now, bits of food caught in my overgrown neckbeard"
a man who is socially inept and physically unappealing, especially one who has an obsessive interest in computing.
"people expect me to be some sort of balding, overweight neckbeard"