switchblade

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++switch·blade /ˈswɪtʃbleɪd/ noun [countable]  a knife with a blade inside the handle which springs out when you press a button 弹簧（小折）刀 →5 see picture at 见图 knife1

Examples from the Corpus

switchblade• He once pulled a switchblade on his director because they couldn't agree on the way to do a scene.• Lucy looked down and realised that she was still carrying the switchblade.• I pulled the switchblade out of my pocket and pressed the button.• The switchblade fell from his hand as he sagged to the ground, whimpering softly, his hands clutched between his legs.

switch·blade nounChineseSyllable  

Corpus the out blade which knife springs a inside with handle a

switchblade
switch‧blade /ˈswɪtʃbleɪd/ noun [countable]
a knife with a blade inside the handle which springs out when you press a button

switch·bladeBrE /ˈswɪtʃbleɪd/ 🔊NAmE /ˈswɪtʃbleɪd/ 🔊 (especially NAmE) (BrE also ˈflick knife) nouna knife with a blade inside the handle that jumps out quickly when a button is pressed 弹簧刀