Shalom
In general, one uses the word "shalom" as the short form of the sentence "Shalom Aleichem" (exactly  "Peace is with you") that can be translated as "good day (morning, afternoon, high noon,...)" (a greeting). This is very similar to the Arabic phrase "Salam Alaykum" (سلام عليكم) which is again a greeting meaning "Peace be with you".