Je was op zoek naar: switchblade (Engels - Japans)

switchblade.
飛び出しナイフ

lieutenant, look at this! a switchblade!
これを見てナイフだよ

wait a minute, did you brought your switchblade?
どこに隠した？

i thought we compared the switchblade to lucy's wound when it came in.
もうナイフは比較したでしょ？

he arched his back, hissed like a rattlesnake and sprang out his claws like a switchblade.
腰を曲げ蛇のようにシューと唸った 鋭い牙を見せた。

but the extent of the bone fragmentation around the wound suggests the tip of the weapon wasn't as sharp as that or the switchblade, for that matter.
ナイフのように 鋭くないはずだ

on a nice spring day, when jan was digging in the sandbox in the backyard, he found a small box. in the box was a shining switchblade with a mysterious inscription.
良く晴れたある春の日に、ジャンが裏庭の砂場を掘っていると、小さな箱を見つけた。箱の中にはぴかぴかの飛び出しナイフが入っており、不思議な刻印が入れてあった。