The phrase "island continent" refers to a landmass that is both an island and a continent on its own. It implies that the land is big enough to qualify as a continent but stands alone and is surrounded by water, making it an island. Full definition
1) How did the marsupials on the isolated island continent of Australia make it to the ark? (religion.blogs.cnn.com)
That effort involved 40 days and nights of rain to drown every single living thing except good fish and that which boarded a large wooden boat and dispersed themselves on island continents thousands of miles from where the boat eventually landed. (religion.blogs.cnn.com)
From the uber cool Melbourne and stunningly scenic Sydney to the mesmerising landscapes of the Outback, this gigantic island continent is fizzing with more incredible sights and experiences than you can shake a didgeridoo at. (gapyear.com)