Meaning
Two nearly opposite things, told apart by tone. In its old sense, 'wicked' means evil, cruel, or oppressive — as in the Rasta charge against 'wicked' Babylon and its 'wickedness'. But in slang praise, 'wicked' means excellent, brilliant, or first-rate — a 'wicked tune', a 'wicked goal'. So the same word can damn or celebrate, and only the context tells you whether wickedness or high praise is meant.
Examples
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Dat a wicked tune, turn it up!
That's an excellent tune, turn it up!
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Babylon system wicked an oppressive.
The Babylon system is evil and oppressive.
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Him score a wicked goal.
He scored a brilliant goal.
Origin
From English 'wicked'; either evil/cruel, or (slang) excellent — set by tone. See [[bad]], [[dread]].
How it’s used
Either evil/cruel, or (slang praise) excellent — context decides. See [[bad]], [[dread]].