far out!, excl. — Green’s Dictionary of Slang

far out! excl.

also far away!

[the mental ‘space’ entered under the influence of hallucinogens]

amazing! remarkable! wonderful!

1970		D. Mitchell Thumb Tripping (1971) 51: Far out! That’s fantastic.
1975		J. Wambaugh Choirboys (1976) 159: ‘Far out!’ Francis exclaimed as they soared through a cloud.
1980		M. Thelwell Harder They Come 243: Far out [...] Far fucking out.
1993		T. Jones Pugilist at Rest 84: ‘Far out,’ I said.
2006		D. Mitchell Black Swan Green 157: ‘Far out,’ they told me. Saying that’s a craze right now.