在位 is read as ざいい (zaii) and means reign.
ざいい
zaii
げんざいいち
(one's) current position
ある
to be equipped with
ざいにち
resident in Japan (of a foreigner)
ざいがく
attending (school, college, etc.)
ざいりゅう
residing (esp. abroad)
ざいか
country home
ありしひ
while still alive
ざいじゅう
residing
ざいたく
being at home
ざいにん
being in office
ざいらい
pre-existing
ざいきょう
being in the capital (i.e. Tokyo, or formerly Kyoto)