It is actually said as 'are you up for it?' and it means so do you want to or not? like in harry potter and the scorcerers stone. Draco says so are you up for it to harry when he is challenged to a...
'Up' has lots of senses: 1: used up; 2: (usually followed by `on' or `for') in readiness; 3: nearer to the speaker; 4: getting higher or more vigorous; 5: open; 6: raise; 7: to a more central...
The opposite of DOWN.
1. From a lower to a higher place. 2. In, at, or to a higher place or position. 3. To a higher point or degree. 4. On one`s feet; in an upright position.