What does "spaceman" mean?

An astronaut, often a male astronaut.

What is a synonym for "spaceman"?

Common synonyms include: astronaut, alien, cosmonaut, rocketman, space adventurer, space traveler.

/ˈspeɪsˌmæn/ noun, slang

noun, slang ·Moderate ·College level

Noun

1
An astronaut, often a male astronaut. childish, informal
"I want to be a spaceman when I grow up."
2
a male person trained to travel in a spacecraft wordnet
3
A humanoid extraterrestrial. informal
"A spaceman from Mars could easily pick out the most civilized nations here. They are the only ones who know how to make atom bombs."

"The spaceman looked out of the space shuttle and saw a little green spaceman in a spaceship."

From space + -man.