Green’s Dictionary of Slang

usu. of an individual, perfect, ideal, delightful, beautiful.

1915		Sport (Adelaide) 8 Jan. 5/4: Just fancy, dreamy Olly B without a Johnny.
1956		K. Amis letter 8 Oct. in Leader (2000) 483: He passed over the slim dreamy freckled lascivious Heather Harding.
1960		J. Havoc Early Havoc 16: ‘I had a dreamy dinner — no expense’.
1962		Mad mag. Dec. 36: Did you notice that dreamy Carl Klutz?
1965		q. in T. Spicer Good Girl Stripped Bare (2017) 4: ‘I’m at the intersection of that yummy fur shop that’s having a clearance in peschaniki muffs and that darling boutique where car sixty-four picked up that positively dreamy hat.”’.
2023		E. Brand on Bluesky 24 Sept. 🌐 Oh wow that [i.e. a well-preserved document] sounds dreamy. I once spent hours trying to transcribe one and then it turned out to be a legal dispute about turnip fields .