outfield
Baseball term for the grassy area beyond the infield. Contrasts with 内野 (infield).
See also: 内野 (ないや)
He is good at fielding in the outfield.
Abbreviation of 外野手. Refers to a player positioned in the outfield.
See also: 外野手 (がいやしゅ)
The outfielder caught the batted ball.
outsider; third party; onlooker
Figurative use derived from the baseball sense. Refers to someone not directly involved in a matter, often used in expressions like 外野から口を出す (to butt in from the sidelines).
This isn't a matter for outsiders to nitpick.
Don't butt in from the sidelines.
In high school, he played outfield.
The fans were cheering from the outfield bleachers.
I wish people not involved would stop butting in from the sidelines.
The batter hit the ball out to the outfield.
部外者 refers to someone who is formally not a member of a group, whereas 外野 used figuratively refers to people who comment on a matter from outside without direct involvement.
傍観者 emphasizes passively watching a situation without acting, while 外野 used figuratively implies onlookers who actively voice opinions from the sidelines.
外野 refers to the outfield area itself, whereas 外野手 refers to the player who plays there.
Compound of 外 (outside) and 野 (field). The baseball senses are calques from English, while the figurative 'outsider' sense is a native extension.
If you worry too much about what onlookers say, you lose the ability to judge for yourself.