One's most heartfelt, sincere condolences. Sometimes said as a set response to someone sharing their misfortunes. A: "I'm not going to be able to come in to work today. I just found out that my father passed away." B: "My deepest sympathies—please, take all the time that you need." We were so saddened to hear about the passing of your sweet brother. Please send our deepest sympathies to the rest of your family.