ἰδνόομαι

A. bend oneself, double oneself up, esp. for pain, ἰδνώθη Il. 2.266; ἰδνώθη δὲ πεσών 13.618; ἰδνωθεὶς ὀπίσω, of a snake in the clutches of an eagle, 12.205; also, of one throwing up a ball perpendicularly, Od. 8.375, cf. APl. 4.97; of the womb, ἢν . . ἰδνωθῇ Hp. Mul. 1.2; ἰδνοῦται ib.10:—Act., ἰδνῶ only in Hdn.Gr.1.451.
Liddell, Scott & Jones
A Greek-English Lexicon, 1940
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