Shanti (Pali: Santi) simply means “peace”. It’s a beautiful meaning and also a very beautiful sound. The shanti is repeated three times, as are many chants in Buddhism. In Buddhism as well as in Hinduism the threefold Shanti is generally interpreted as meaning the Threefold Peace in body, speech, and mind (i.e. peace in the entirety of one’s being).
Hindu teachings typically end with the words Om shanti shanti shanti as an invocation of peace, and the mantra is also used to conclude some Buddhist devotional ceremonies.
Source (A great online meditation center)