69 sex position
In this position, the two individuals generally lie down, one on top of the other or side to side. However, instead of lying face to face, each places their head next to the other's genitalia, enabling the genitalia of both partners to be orally stimulated at the same time. Alternatively, a similar position can be taken by one upright and one inverted individual. Thus, they are upside-down relative to one another, like the numbers '6' and '9' in '69', hence the name.