To be up to

To be equal to, or prepared for; as, he is up to the business, or the emergency.
- H. Spencer.
To be engaged in; to purpose, with the idea of doing ill or mischief; as, I don't know what he's up to.

See also: Up, Up

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
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