lubricate
To make something slippery. A more erotic explanation would be to make the penis or vagina more slippery and hence achieve a better rubbing feeling when the sex organs are rubbing against each other. Men produce a lubricant called precum while women secrete vaginal fluid that makes the vagina walls wet.
Example:
To enhance a better sex experience both partners secrete lubricants that lubricate their respective sex organs.
To enhance a better sex experience both partners secrete lubricants that lubricate their respective sex organs.