The act of wrapping the penis around the sac-region. Thus, giving off the appearance of a snake wrapped around a bush. Also, the term reflects the aggression of the penis as a snake and protecting its "two best friends" from the vagina.
A snake in your bush is a term for when there is a cock in your vagina. The cock is the snake the vagina is the bush. Bam there you go. Now you know. The more you know. Oh god how do I know this shit.