Skrev

Pronounced (skrɛv).
Unwashed, poorly educated (or low IQ), impoverished, diseased, substance-abusing person of ill repute. Similar to a smack-rat or crackhead, but less specific; where the nature of the substance abuse is not yet established or the person isn't a frequent user of a specific drug, but will take anything they can get their hands on.

John is such a skrev.

Don’t go down that alley, it’s full of skrevs.