inerm

Adjective

 * 1)  Without spines or thorns; inermous.
 * 2) * 1926, South Africa. Dept. of Agriculture. Division of Veterinary Research, Report (volumes 11-12, page 79)
 * The cirrus is inerm and slender, measuring 0.1 mm. in length and 0.02 mm. in diameter.

Etymology
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Adjective

 * 1) defenceless