This is the 8473rd most frequent Polish word.
poniewieża
"Poniewieża" is not a standard Polish word. It may be a misspelling or misinterpretation. If you meant "ponieważ," it translates to "because" in English.
Here, 'poniewież' is used as a causal conjunction connecting the reason for not attending the meeting.
Nie mogłem przyjść na spotkanie, poniewież byłem chory.
I couldn't come to the meeting because I was sick.
In this sentence, 'poniewież' works to specify the motivation behind the action performed by the subject.
Powiedział mi to, poniewież uważał, że jest to ważne.
He told me this because he thought it was important.
Here, 'poniewież' introduces a temporal consequence acting upon the circumstance described.