क्विपि

Source: nityAnandaH

The feminine of विश्वजित् is विश्वजित् itself. Similarly, the feminine of वेदविद् (वेदवित्) is वेदविद् (वेदवित्) and the feminine of धारामुच् is धारामुच्.

Also, if you can enlist the sūtras used for making their forms then it woud be added help.

The reason why the feminine forms for the above words are the same as the masculine forms is that none of the rules in the स्त्रीप्रत्ययप्रकरण (4.13 to 4.1.81) are applicable to them. All three are kvibanta words, with the kvip suffix. For most (but not all, see below) kvibanta words, the feminine form is the same as the masculine (and neuter) form.

For example, the following feminine kvibanta words are feminine—श्रीः, सूः, प्रसूः, उपनिषद् (उपनिषत्), परिषद् (परिषत्), उपानह् (उपानत्), सम्पद् (सम्पत्), आपद् (आपत्), विपद् (विपत्), etc. No feminine suffix is ordained after the क्विप् suffix in these words.

The same is true for words like उखास्रत्, पर्णध्वत्, etc., where the feminine form is the same as the masculine form (उखास्रद् ब्राह्मणी, पर्णध्वद् ब्राह्मणी, examples cited by Patañjali in the Mahābhāṣya). The ङीप् which would have occurred by उगितश्च (४.१.६) is blocked by धातोरुगितः प्रतिषेधो वक्तव्यः (वार्तिक on ४.१.६).

There are some kvibanta words which do take a feminine suffix. For example, the feminine forms of प्राञ्च् (प्राङ्), प्रत्यञ्च् (प्रत्यङ्), सम्यञ्च् (सम्यङ्, सम्यक् in neuter gender), उदञ्च् (उदङ्), अर्वाञ्च् (अर्वाङ्), अवाञ्च् (अवाङ्), उरुव्यञ्च् (उरुव्यङ्), सध्र्यञ्च् (सध्र्यङ्) are प्राची, प्रतीची, समीची, उदीची, अर्वाची, अवाची, उरूची, सध्रीची, respectively. These kvibanta words get the ङीप् by अञ्ञ्चतेश्चोपसंख्यानम् (वार्तिक on ४.१.६). As per the Vācaspatya, the feminine forms of असुरहन्, सपत्नहन्, etc. are असुरघ्नी, सपत्नघ्नी, etc. (e.g., शतपथब्राह्मणम् १.१.४.१४: मनोर्ह वा ॠषभ आस … तस्मिन्नसुरघ्नी सपत्नघ्नी वाक्प्रविष्टा). In these cases, the kvibanta word gets ङीप् by ऋन्नेभ्यो ङीप् (स्त्रियां नान्तत्वात् ङीप्, Vācaspatya, referring to ४.१.५ ऋन्नेभ्यो ङीप्). I cannot think of any more examples right now.