Green’s Dictionary of Slang

wonderful, marvellous.

1970		T. Southern Blue Movie (1974) 73: ‘Terrif, Nicky,’ said Sid, ‘terrif!’.
1988		R. Doyle Commitments 58: Terrif, said Joey The Lips.
1995		J. Stahl Permanent Midnight 231: But, hey, thanks . . . you’re really terrif!