Ostrich/ˈɑːstrɪtʃ/ Definition 1 of 2Pro Tip 1/3Speed reference Ostriches are known for their speed, often alluded to when comparing fast runners. He's as quick as an ostrich on the racetrack. Pro Tip 2/3Flightlessness Despite being a bird, ostriches cannot fly, which can be surprising. Despite its wings, the ostrich cannot take flight. Pro Tip 3/3Large size Ostriches are the largest birds, used to describe something unusually big. My suitcase is like an ostrich, towering over the others.