The verb 'sling D' is a compound verb composed of 'sling,' which means to sell drugs and 'D,' which stands for dick, dong, ding-a-ling (see also 'wee wee').
Literally, to Sling D means to peddle ones cock, i.e. to have sex. The use of 'Sling D' also brings with it the connotation of
having sex on an
operational level or on a mass scale, as if pulling down bitches was one's job.
After Robert got
new job,
finally got in shape, and moved into a pent house
apartment, he knew he would now be able to sling D all over town.