Green’s Dictionary of Slang

(US) wholly wrong, greatly mistaken.

1959		M. Summerton Small Wilderness 112: You’re way out, Puss. If anybody has got a perfect alibi [...] it’s Cliff [OED].
1965		W. Dick Bunch of Ratbags 169: Some psychologists had been studying us bodgies and widgies and boy, were they way out! [...] We reckoned if they didn’t like these things, they were square for sure. They were way-out daddy-o.
1975		Sun. Times Mag. 12 Oct. 80: I’ve been way-out over some issues [...] but I’m not a way-out politician.