noun
A formal, literary term for one's own wife or a wife in general. In modern Japanese, 妻 (つま) or 奥さん (おくさん) are far more common.
彼は妻室を伴って式典に出席した。
He attended the ceremony accompanied by his wife.
Compound of 妻 (sai, 'wife') and 室 (shitsu, 'room'), originally referring to the wife's quarters and by extension the wife herself. The exact historical derivation is uncertain.