Most commonly practiced before a night taking the Commo out to Chapel Street, downing a slab at Bazza's place, or hitting the drags at Dandy.
"The Ranga got Neknominated, the weak dog only downed a double black!".
Someone who is neknominated has 24 hours after nomination to mix together a variety of spirits (and whatever else they deem worthy/disgusting/difficult) and post a video of chugging it in one go. After necking your drink you then nominate at least one other person.
"Cheers for the neknomination submarine guy... (sculls a pint of Two Brothers Grizz)... I now neknominate Charles Barkley and David Schwimmer.