Japanese does not have the sound 'si'. The closest sound to that is 'shi'.
According to freedict.com japanese dictionary,
- shi luxury, pride, extravagance, arbitrariness
- shi official, civil service
- shi offspring (animal)
- shi four
- shi calling card
- shi city
- shi death, decease
- shi records, document, magazine
- shi order, sequence, times, next, below
- shi recollect, remember
are some possible meanings.