Green’s Dictionary of Slang

rapid adj.

(Irish) a general term of approval, excellent, wonderful.

[Ire]R. Doyle Commitments 45: You’re Declan Blanketman Cuffe. —That’s a rapid name, said Outspan.
[Ire]F. Mac Anna Last of the High Kings 107: I’ll borrow me Pa’s Jag. We’ll have a rapid time.
[Ire]G. Coughlan Everyday Eng. and Sl. [Internet] Rapid (a): amazing.