In addition; also; at the same time—though the proper spelling is 'as well' as two words.
This is a modern misspelling or variant of 'as well,' which comes from Old English 'as' (in the manner of) and 'well' (in good measure, thoroughly). The phrase emerged when these two words began functioning together as a single adverbial unit.
This is a case where internet language and text-speak have created a 'word' that most dictionaries don't recognize separately—it's grammar evolution in real time, showing how people naturally run words together when typing quickly.
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