Green’s Dictionary of Slang

cosmic adj.

[SE cosmic, i.e. the contemporary interest in psychedelic drugs]

excellent, first-rate, perfect, overwhelming.

[US]W. Murray Sweet Ride 37: Cosmic let downs, chickie. Absolutely cosmic betrayals. Lousy breaks.
[US]C. McFadden Serial 42: It was cosmic of Kate to flash on it like that.
[UK]J. Sullivan ‘A Slow Bus to Chingford’ Only Fools and Horses [TV script] No, that is cosmic Janice. No really – no that is cosmic that.
[UK]Guardian 31 July 21: Bailey’s Beads shining through the valleys of the moon! Cosmic!
[UK]Guardian Rev. 10 Mar. 2: Hey! Wow! Cosmic!