n.spontaneous removal or casting off of a body part (as the tail of a lizard or claw or a lobster) especially when the organism is injured or under attack
英汉双解大词典
autotomy/ɔːˈtɒtəmɪ/
1.
N（名词）
the casting off by an animal of a part of its body, to facilitate escape when attacked 自割; 当动物遇到攻击时为逃脱而引发的自身部位的脱离