Green’s Dictionary of Slang

1. to pass, esp. to hand over drugs.

2015		67 ‘Hashtag’ 🎵 What's all the talk like me and my man weren't tryna dash stones.
2017		theculturetrip.com ‘Guide to London Slang 10 Jan. 🌐 Dash – to dash is to pass something to somebody (drugs) – but it can be ‘pass’ too.

2. to throw away, discard.

2020

G. Krauze What They Was 13: He tells me to dash the black American Express card [...] I pretend to drop the card.