iron-backed
From LSJ
οἱ Κυρηναϊκοὶ δόξαις ἐχρῶντο τοιαύταις: δύο πάθη ὑφίσταντο, πόνον καὶ ἡδονήν, τὴν μὲν λείαν κίνησιν, τὴν ἡδονήν, τὸν δὲ πόνον τραχεῖαν κίνησιν → the Cyrenaics admitted two sensations, pain and pleasure, the one consisting in a smooth motion, pleasure, the other a rough motion, pain
