What Does Spliff Mean?
A spliff ("split the difference") is a type of cannabis cigarette rolled with a mixture of tobacco and marijuana, while blunts (though wrapped in a tobacco leaf) and joints typically only contain weed.
Spliffs often use a high ratio of cannabis to tobacco, but when kief or hash is used or if the cannabis is of high quality, the ratio can be decreased to conserve. They are traditionally rolled into a conical-style shape with rolling paper or even in cigarettes.
Sometimes, the term ‘spliff’ is also just used to refer to a really nice, well-rolled joint. It may also be confused with the term 'sploof'.
Maximum Yield Explains Spliff

Spliffs are popular is because they are discreet. The tobacco tends to cover some of the smell of the cannabis, thus making it seem like you’re just smoking a normal cigarette. Also, since tobacco is added to the cannabis, the cerebral effects of smoking a spliff are less potent. However, this again depends on the ratio of weed vs. tobacco used in them. Not all spliffs are created equal; some taste like a traditional cigarette, while others have an added depth to the flavor profile.
Spliffs, unlike joints, do not self-extinguish and do not canoe (meaning one side does not burn faster than the other) due to the added tobacco, which fills in air pockets within the ground marijuana. On top of that, spliffs save up your stock of weed since it is mixed with tobacco.