Hoshi (Successor) (法嗣)
"Hoshi" (Hassu) refers to a successor of his/her master's teachings.
Through Shishisosho (the transfer of a master's teaching to a disciple), this person receives Buddha's Dharma and Inka (a Certification of spiritual achievement) from his/her master, and then passes that on to his/her disciple. He/she is a Buddhist disciple. It is a term used mainly in the Zen Sect and Esoteric Buddhism.
In the Zen Sect, it is pronounced 'Hatsusu' or 'Hassu.'
It is occasionally pronounced 'Hosshi' as well.