Union, merger with the Divine. (Glossary for the Vahinis)

Sayujya -  complete oneness with the Divine. (SSS Vol.22)

Sayujya is complete integration or merger with the Lord. This is the end of all sadhanas (spiritual exercises). (SSS Vol.32 Part I, p. 183)

It is only when all trace of difference disappears, and unity is attained that the highest stage is reached. This is what is called Sayujya. This comes of Divine Grace, won by the Essence of the sadhana of each. It cannot be claimed as the fruit of effort. The Bhakta will aspire for this merging or Aikyam. He wishes to serve the Lord as he pleases and to experience the joy of the Form which he has attributed to the Lord. But the Lord out of His Grace, gives him not only Salokya, Samipya and Sarupya but also, Sayujya! (Prema Vahini, p. 96)