jerk (jerks plural & 3rd person present) (jerking present participle) (jerked past tense & past participle )
1 verb If you jerk something or someone in a particular direction, or they jerk in a particular direction, they move a short distance very suddenly and quickly.
Mr Griffin jerked forward in his chair... V adv/prep
`This is Brady Coyne,' said Sam, jerking his head in my direction... V n adv/prep
Eleanor jerked her wrist free... V n adj
Jerk is also a noun., n-count
He indicated the bedroom with a jerk of his head.
2 n-count If you call someone a jerk, you are insulting them because you think they are stupid or you do not like them.
INFORMAL, OFFENSIVE, disapproval
knee-jerk
If you call someone's response to a question or situation a knee-jerk reaction, you mean that they react in a very predictable way, without thinking. adj ADJ n (disapproval)
The knee-jerk reaction to this is to call for proper security in all hospitals.