the 5th wheel is the spare wheel attatched to the back of a slab. the 5th completes the slab. without it you are not ridin slab. it can often be seen in a tilted or "reclined" position.
Predominately used to refer to 4x4 ATVs but may refer to any motorized off road vehicle (i.e., snowmobile, sand rail) which allows non-athletic couch potatoes to get into backcountry places they typically would never consider getting to through their own physical exertion and exercise. Likelihood of driver being from Texas is disproportionately high. They are particularly found in the mountains and deserts of Colorado, Utah, Oregon, and California.
The term is often used by real outdoorsy people as a sign of irritation and disgust. See below examples.
Did you see what those assholes in the Texas Wheelchairs did to our favorite hiking trail? Why don't they just get off their fat lazy asses and walk or bike up here?
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.