Kayak/ˈkaɪæk/ Definition 1 of 2Pro Tip 1/3Outdoor Activity Used to refer to an outdoor water sport, often for recreation or exercise. During summer, kayaking is my favorite outdoor activity. Pro Tip 2/3Watercraft Shape A kayak is narrow and elongated, differing from a wider, circular boat. The kayak cut smoothly through the water with its sleek shape. Pro Tip 3/3Adventure Travel Kayaks are often used in adventure travel or eco-tourism contexts. Our vacation package includes a guided kayak tour through the mangroves.