Green’s Dictionary of Slang

drag adj.2

(US) boring.

M. Braun Love Me Do 14: ‘We had a great hip English master and instead of keeping us to the drag stuff [...] he would let us read Tennessee Williams’.
[US]‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 30: party pooper – A drag person; a cat or bird who is not a swinger.
[UK]M. Novotny Kings Road 80: ‘I know she’ll bore you but just treat her as a joke.’ ‘She’s a real drag doll’ moaned CB.
[US]Eble Campus Sl. Mar. 2: drag – boring, uninteresting.