Originally, it was a somewhat common mispelling of the word "brother", often by baby boomers, people attempting to imitate Hulk Hogan, and Fudds. It's now used often to troll people, and is used as a mild joke when shitting on boomers in gun communities, and biker communities. It's also especially popular on /k/, other boards of 4chan, when adding complete silliness to a post.

A man that surpasses the title of brother, a man who is so lordly that a word must be made to describe him.

Borther - a brother cousin, or other incestuous male relatives.

Borther is a word that can mean many thing but is often used to refer to friends and relatives

Something you sick on a tall, creepy man who is stalking you.

Like a brother but some stupid little shit couldn’t pronounce it right

Heck yeah borther: a phrase that started on YouTube, under the gaming channels Kryoz and SMii7Y. It’s more common on Kryoz’ channel, but is still often prevalent on SMii7Y’s, as well. It’s spoken in a southern accent, a simple mispronunciation of “heck yeah brother.” This phrase is a definite fan favorite.