A river nigger is a Mexican as they use the river to cross over to the USA and jump fences or cross at openings in fences to gain access to the USA. A fence jumper, if you will.
An expression used in the card game "Texas Hold 'em Poker" for someone who was losing the hand to one or more players, and was saved by the 5th card, the river, due only to luck, and won the hand.
Bob: "haha, I'm beating you with the odds of 4:1 in favour of me, you only have 3 cards you can hit out of the deck, with one card left, what a crappy call and a horrible read"
A "human" that spends so much time playing video games that their posture is level nerd neck. Everytime anyone goes tryhard they hunch down and their neck gets longer there fore a nerd neck is always hunched down cause they're always going try hard. In other words a nerd neck is a try hard, since their neck is 100% longer than the average human being due to playing too many video games and taking them serious, nerd necks are not even considered human anymore but something more sad. Nerd necks are often found on fortnite, their natural habitat usually being tilted towers.