Green’s Dictionary of Slang

1. (US) an escape, a withdrawal.

1947

T. Thursday ‘Billy the Kidder’ in Blue Ribbon Western Nov. 🌐 At that, me and McGinty edge toward the sidewall canvas, for a quick duckout.

2. a failure, something that fails a test.

2001

N. Barlay Hooky Gear 65: Unveil the soaked tarp off of a recent MOT duckout thats most likely been cut an shut with a ringed an clocked scrapyard reject.