what is a DL#
Definition of DL. 1  DL is short for down-low, which basically means to keep things under-wraps, to keep a secret or lay low. 2  I'll tell you this, but, you gotta promise to keep it on the DL. D.L. means down low. it means that something is not known to all. if you keep something on the D.L... 2  you don't share it with others. 3  I don't want my Dad to find out, so keep it on the D.L. 4  She like me but keep that on the DL.