Sister/ˈsɪstər/ Definition 1 of 5Pro Tip 1/3Family Bond Used to express a strong family relationship with shared life experiences. My sister and I have cherished childhood memories. Pro Tip 2/3Age Relative Specify 'older' or 'younger' to indicate the sister's age relative to another sibling. My older sister is starting college this fall. Pro Tip 3/3Twin Connection Mention 'twin' to highlight a unique bond and the fact of being born at the same time. My twin sister and I look almost identical.