As a Hindi name
ओष्ठ · noun · masculine
होंठ । ओंठ । लब · दो या दो संख्या का सूचक शब्द — Śabdasāgara
ओष्ठ · oshṭh · s.m.
Lip (especially the upper; see hoṅṭ) — Platts (1884), digital edition courtesy DSAL, University of Chicago, p. 105
As a Sanskrit word
Meaning
the lip (generally du.), &c.
Verified derivationWhy this matches what you typed
The spelling you confirmed, ओष्ठ, is itself a dictionary headword — no grammatical transformation stands between what you typed and the meaning above.
Dictionary citations
oṣṭha m. (etym. doubtful; √ uṣ, Uṇ. ii, 4) the lip (generally du.), RV. ii, 39, 6; AV. x, 9, 14; xx, 127, 4; VS.; ŚBr.; Mn. &c.
the forepart of an Agnikuṇḍa q.v., Hcat.
oṣṭha [cf. Zd. aoshtra; O. Pruss. austa, ‘mouth’; O. Slav. usta, ‘mouth’.]
oṣṭha m. (-ṣṭhaḥ) The lip, especially the upper, &c. du. m. (oṣṭhau or oṣṭhādharau) The lips: see adhara. f. (-ṣṭhī) A creeper, bearing a red flower, to which the lip is commonly compared, (Bryonia grandis.) E. uṣa to burn, than Uṇādi affix, fem. affix ṅīṣ: see vimba.
Caveats
Sources contain errors and engines have limits; every claim above carries its citation so you can verify it. This is guidance about names and their sources — not religious or astrological consultation. How we work · Our sources