A facility for launching and receiving spacecraft, analogous to an airport for space travel.
In the future, trips to the moon from spaceports may become common.
宇宙基地 is a broader term for a space station or base in space, whereas 宇宙港 is the launch and landing facility on Earth (or another celestial body).
Compound of 宇宙 (uchū, 'space') + 港 (kō, 'port'). A relatively modern term modeled after 空港 (kūkō, 'airport').