Abbott-Smith Manual Greek Lexicon
σκληρός (G4642)
5 σκληρός , -ά, -όν ( σκέλλω , to dry ), [in LXX chiefly for קָשָׁה ;] hard to the touch, rough, harsh , (opp. to μαλακός ); metaph., in various uses; of men, hard, stern, severe : Mt 25:24 ; of things, hard, rough, violent : σκληρόν σοι ( ἐστι ), Ac 26:14 ; λόγος , Jo 6:60 ; ἄνεμος , Ja 3:4 ; σκληρὰ λαλεῖν , Ju 15 .† SYN. : αὐστηρός , q.v
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain