In tennis and other knockout tournaments, the organisers pick the strongest players and give them numbers — first seed, second seed, and so on — so that the top players are kept apart in the draw and cannot meet until the later rounds. A player who is not given one of those numbers is unseeded. It says nothing about whether they are good; it says the organisers did not rank them among the chosen few, usually because their world ranking is lower or they are coming back from injury. Sports writers love the word precisely because unseeded players sometimes win, and 'unseeded' in a headline carries a quiet thrill of the underdog. You will meet it most in tennis, and also in badminton, table tennis and chess. In gardening the same-looking word means 'with no seeds planted', but that use is rare and you will almost never be confused in practice, because the context is so different.

非種子（選手）；未列為種子的。台灣網球、羽球報導直接說「非種子選手」，跟「第一種子」「地主種子」相對。中文的「種子」不是植物的意思，是排名前列、被特別分開安排的選手。