A kind of Siddha (liberated soul);
that Siddha, who had attained emancipation in the form of a Tirthankara (ford-founder).
risabhādayo titthakarā, tejamhā titthakaraṇāma-kammudayabhāve ṭhitā titthakarabhāvāto vā siddhā tamhā te titthakarasiddhā.
(Nandī 3l Cū p. 26)