skin-popping

The practice of injecting drugs under the skin instead of directly into the bloodstream/vein. This is absolutely retarded as the effect cannot compare to the intravenous method, in addition the potential for infections that could dime the user out as professional medical attention will be required to circumvent the potential possibilities of much worse discomfort. In regards to injecting drugs it is the product of a missed injection, instead of into the circulatory system the solution is deposited anywhere else under the skin. This is not good as it is a possibility that this accident could potentially transform into cellulitis, and then there is a chance of an abscess. See further medical texts for the specifics, however it is not out of the realm of possibility this accident could result in loss of limb, or even loss of life. Ending on a positive note however, its much more likely you'll be sore at injection sight with some minor swelling, redness. Keep an eye on it and be more careful next time.

Injecting into skin, not into veins or muscles or anything. It is not the best way because some drugs get lost in your tissues so the effect is not as strong, and you're more likely to get absesses this way.

sticking a needle into your skin

Injecting heroin WITHOUT DIRECT INJECTION into a vein.

throwback word of the seventies... injecting heroin into your veins with a needle.