Dictionary Definition:
sā́dhiṣṭha mfn. (superl. of sādhu) straightest (as a path) RV
• most effective (as a sacrifice) ib
• very fit, most proper or right ChUp
• hardest, very hard or firm (= dṛdha-tama
• in these senses regarded as irreg. superl. of bāḍha Pāṇ. 5-3, 63) L