In the wizarding world, the term Kiss holds a dual meaning. It refers to the conventional, mundane act of affection between individuals, several of which are pivotal to the character relationships and subplots of the series. More ominously, it is the common term for the Dementor's Kiss, the most terrifying act performed by a Dementor, which involves sucking the soul from a victim's body.
The Dementor's Kiss is the ultimate punishment and attack of a Dementor. It is considered a fate worse than death. The Ministry of Magic has authorized its use on convicted criminals, such as in the case of Barty Crouch Jr..
The only known defense against a Dementor attempting to perform the Kiss is the Patronus Charm (Expecto Patronum). A powerful, fully-formed corporeal Patronus is required to drive away a Dementor that is close enough to use its ultimate weapon. While chocolate is an effective remedy for the general chilling effect of a Dementor's presence, it offers no protection against the Kiss itself.
Beyond the Dementor's Kiss, several non-magical kisses are significant milestones in the personal lives of the characters.