d.l., adv. — Green’s Dictionary of Slang

d.l. adv.

(US black) in a clandestine, sneaky manner.

1994		G. Smitherman Black Talk.
1995		L. Stavsky et al. A2Z 28/2: d.l. – adv. down low, as in low profile or hidden.
2013		T. Robinson Hard Bounce [ebook] ‘Shhh!’ I waved at him to keep his voice down. ‘DL, stupid. DL’.

on the d.l.

surreptitously, clandestinely.

2012		M. Lacher On the Bro’d 8: [O]n the DL he was already pretty close to pimp status.
2014		B. Koeler ‘Be My Alibi’ in ThugLit Sept. [ebook] You tell them you like to hook up with guys on the DL.