Noun
Someone or something that jiggles.
(slang) A key, now especially a car key, that has been partially ground down so that it will open many locks.
Source: en.wiktionary.orgSee, older models of pressure cookers have what's called a "jiggler": a weight that sits on top of a steam vent. Source: Internet
Moreover, the only way you can monitor internal temperature is by adjusting the heat until the jiggler releases steam at a bare hiss, indicating that you've achieved and maintained good pressure inside. Source: Internet