Green’s Dictionary of Slang

raspberry v.

[raspberry n.]

to deride, to dismiss.

[US]C.B. Chrysler White Slavery 70: No ‘dick’ has anything on you. And if you’re you get nicked for ‘laughing’ you can ‘raspberry’ the ‘bull’ and get ‘sprung’.
[UK]P. Larkin letter 19 Sept. in Thwaite Sel. Letters (1992) 45: If I’d composed a poem like that one I’d keep it jolly dark, my God I would. Ought to have been duly raspberried by all concerned.