Green’s Dictionary of Slang

neato adj.

[SE neat + -o sfx (5)]

(US teen) good, excellent, a general term of approbation; often as excl.

[US](con. 1918) S. Longstreet Pedlocks (1971) 257: The meal was sure neato, sir.
[US]N. Giovanni ‘A Revolutionary Tale’ in King Black Short Story Anthol. (1972) 24: I have this really neato pink IBM.
[US]R. De Christoforo Grease 150: He’s neat-o.
[US]S. King Tommyknockers (1989) 232: But look! Neat-o, huh?
[US]R. Crumb Zap Comix 13 in Coffee Table Art Book (1997) 25: Oboy! Neato! Just what I wanted!
[US]Eble Campus Sl. Apr. 6: neato – interesting, intriguing.
[NZ]McGill Reed Dict. of N.Z. Sl. 141: neat as/neat, eh?/neato Pleasing. ‘Like my jumper? Neat as, eh?’ Local variants of US ‘neat’, for anything impressive to teens, popular ANZ from later C20.

In exclamations

neato jet! (also neato torpedo!)

(US teen) extremely excellent! absolutely wonderful!

[US]Eble Campus Sl. Mar. 4: neato torpedo – fantastic, super.
Hearth & Leisure on Highest And Best Use [Internet] If you think the Steer Grill is neato-jet, you gotta see the Wild Boar model that the folks from Traeger custom built for H.I. Hearth & Leisure.