汰 almost never appears alone in modern Chinese. You'll meet it in compounds:
淘汰 (táotài, 'to eliminate / weed out' — the most common),
汰换 (tàihuàn, 'to replace / phase out'),
优胜劣汰 (yōushèng-liètài, 'survival of the fittest, lit. the superior wins, the inferior is weeded out').