Grounded means forbidden to go out, as a punishment from your parents. Grounded for a week, you are grounded, being grounded.
It is chiefly American in origin and thoroughly established everywhere now. The image comes from aviation: a grounded aircraft is one not allowed to fly, which is the other main sense — all flights were grounded. Of a person's character, grounded means sensible and unaffected by success: she has stayed very grounded. And in electricity, grounded is the American term for what British English calls earthed.
1adjectivegroundedForbidden to go out, as a punishment.
“You're grounded for a week, so no parties and no friends round!”
2adjectiveallowedNot allowed to fly.
“Every aircraft in the country was grounded for three days.”
3adjectivesensibleSensible and unaffected by success.
“He has stayed remarkably grounded through all of it.”
grounded is a state of being kept down.
All the senses come from ground, the earth. To be grounded is to be kept on the earth — as an aircraft, as a teenager, or as a person whose sense of proportion has not left the ground.
Middle English
grounded
English, today
grounded
From Middle English grounded, i-grounded, equivalent to ground + -ed.
Etymology from Wiktionary, CC BY-SA