Snakeheads are Chinese gangs which smuggle people to other countries. They appear often especially in the Fujian region of China and smuggle their "customers" often into more wealthy Western countries like the United Kingdom or the United States.
The name snakehead comes from the people being smuggled, often called "man-snake" in the Chinese language. The people who organize the smuggling are therefore called snakeheads (head of (man-)snakes), which is in fact a word-by-word translation of the Chinese term
When your girl is riding you and you finish inside her, then she proceeds to get up and drag the cum over your stomach up to your chest yelling "I'm a snail"
Snakehead is the common name for Channidae, a family of freshwater fish that can breathe air and "walk" on land. While not native to the U.S., snakehead fish have been accidentally introduced into the waters of some states, including Maryland. To snakehead is to arrive at a destination in an unexpected way.
Walking instead of driving, driving instead of flying, crawling instead of swimming are all examples of snakeheading.