Pretty much the same as merk or slew. It is the act of inflicting extreme damage either lyrically or physically to another boi. From the verb to slew, but with "age" stuck on the end to make it seem more gangster. This type of terminology (the use of "age" on the end of words, in this case "slewage") was popularised by gangbangin Brit mc Mr Wong in his riddim "wongage", and is commonly used in virtually every endz of da L-O-N.

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