In English informal speech, French kiss, also known as a deep kiss, refers to an amorous kiss in which the participants' tongues extend to touch the other participant's lips or tongue. A "kiss with the tongue" stimulates the partner's lips, tongue and mouth, which are sensitive to the touch and induce physiological sexual arousal. The oral zone is one of the principal erogenous zones of the body. The implication is of a slow, passionate kiss which is considered intimate, romantic, erotic or sexual. American slang synonyms include "swapping spit" and "tonsil hockey".