Green’s Dictionary of Slang

(US) ostentatious.

1915		O.O. McIntyre New York Day by Day 8 June [synd. col.] The ‘by the sea’ resorts are opening up just now. [...] They are considered quite stunty by the crowds who breakfast at 4 o’clock in the afternoon.
1920		O.O. McIntyre New York Day by Day 26 Oct. [synd. col.] Rich and vapid idlers [...] in their stunty roadsters.