The Collaborative International Dictionary
happy camper
Camper \Camp"er\, n.
One who lodges temporarily in a hut or camp, especially who sleeps in a wilderness for recreation.
A person who stays at a summer camp or day camp.
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A vehicle, such as a small truck, or a pickup truck with a hood over the back, equipped for convenience while camping out.
happy camper a person who is pleased with the situation in which s/he finds him/herself. Often used ironically or in understatement, especially in the negative; as, the passengers left behind on the island were not a bunch of happy campers.
Wiktionary
happy camper
n. (context chiefly US English) One who is thoroughly content or satisfied.