From the MSN Encarta Premium Dictionary online:
http://encarta.msn.com/dictionary_/typhoon.html
ty·phoon [ tī fn ] (plural ty·phoons)
noun
meteorology tropical storm: a violent tropical storm in the western Pacific and Indian oceans
http://encarta.msn.com/dictionary_/hurricane.html
hur·ri·cane [ húrri kàyn ] (plural hur·ri·canes)
noun
1. meteorology severe storm: a severe tropical storm with torrential rain and winds above 119 km (74 mi) per hour. Hurricanes originate in areas of low pressure in equatorial regions of the Atlantic or Caribbean, then strengthen, traveling northwest, north, or northeast.
Since the question specifies the Pacific, I would say the answer would have to be typhoon, wouldn't it???