(1) Prajaa means subjects (people) and Pati means Lord or master, thus Prajaapati means who is the master or Lord of the people. Lord of all creatures - a name in the Ved originally applied to Savitri, Som, Twashtri, Hiranyagarbh, Indra and Agni. Afterwards the name of separate Devtaa presiding over procreation. (Manu, xii, 121), and the bestower of progeny and cattle.

Prajaapati is sometimes invoked as the Creator (Brahmaa Jee), and sometimes as one of the 33 Rishi. It is also a name of the mental sons of Brahmaa who according to Manu (i, 34) are 10 - Mareechi, Atri, Angiraa, Pulastya, Pulah, Kratu, Vashishth, Daksh, Bhrigu and Naarad. Some say that there are 7 Prajaapati (the first 7 sons of Brahmaa Jee).

(2) Name of the 11 atmospheric deities in Rig Ved. The entire hymn (10-121) of Rig Ved is devoted to Prajaapati where this term is used synonymously with God and wherein this is acknowledged in question from stating - "Whom (save Him) shall we worship?" The word Prajaapati is also used in the sense of progenitor. It is therefore applied to Brahmaa, the Creator, and Swaayambhuv Manu, supposedly the first human.

(3) Name of a person who was the descendent of Praanshu (2900 BC).

(4) Name of a Rishi who was the son of Vishwaamitra.
[We have never heard that Vishwaamitra had a son named Prajaapati. His one son's name was Raivya, another son's name was Ashtak who was from yayaati's daughter Maadhavee.]

(5) V-Raamaayan, 1/6 Vashishth Jee gives Vishwaamitra's introduction to King Janak as the son of Prajaapati Kanyaa.

We have heard only these names of Prajaapati --
(1) Daksh Prajaapti - born from Brahmaa Jee. Married to one of the three daughters of Swaayambhuv Manu - Prasooti
(2) Kardam Prajaapati - married to one of the three daughters of Manu - Devahooti.
(3) Ruchi Prajaapati - married to one of the three daughters of Manu - Aakooti.
(4) Kanyaa Prajaapati -
(5) Krishaashwa Prajaapati - V-Raamaayam, 1/6/21 says that Daksh's two daughters, Jayaa and Suprabhaa, were married to Krishaashwa Prajaapati. They produced 50 sons each in weapons form.
(6) Panchjan Prajaapati - his daughter was Asiknee and was married to daksh who was the son of Prachetaa Gan and Maarishaa.