What is the meaning of 天下?

the world; everything under the sky; all under heaven

China; the Chinese nation

society

state power; domination

the whole world, the earth

the whole country, all of Japan

the government of Japan

power, control over the government

the shogun

in traditional Japanese card games, one of the strong cards known as (aza)

short for 天下一 (tenka ichi): the best in the world (often used attributively with the particle (no))

the world, the earth

hanja form of 천하 (world, earth; China)

chữ Hán form of thiên hạ (world)

Source: wiktionary.org