I. up ‧ side 1 /ˈʌpsaɪd/ BrE AmE noun [singular]
especially American English the positive part of a situation that is generally bad OPP downside :
The upside of the whole thing is that we got a free trip to Jamaica.
II. upside 2 BrE AmE preposition
upside the head/face etc American English informal on the side of someone’s head etc