A recursive island (or lake) is an island or lake found within another island or lake - like a little "island-ception"! This fun twist on geography happens when smaller landmasses, like Madagascar or New Zealand, are considered islands, while larger continents are not. So, if an island is located within a lake on one of these islands, it becomes a recursive island! You can dive deeper into this intriguing concept in the Wikipedia article on recursive islands and lakes.