1screw 
/ˈskru:/ noun
plural screws /ˈskru:/ noun [count] 1 : a narrow, pointed metal cylinder that has a wide flat or rounded top and a ridge (called a thread) that goes around it in a spiral ◊A screw is used to hold things together or to attach things. It is inserted into wood, metal, etc., by being turned.
▪ Tighten the screws. — see picture at carpentry; compare 1nail 1 2 : an object that has a thread like a screw which is used to attach or connect it to something — usually used before another noun ▪ The bottle has a screw cap/top. [=a cap/top that is attached and removed by turning it] 3 informal + offensive a : an act of sexual intercourse
b : a sexual partner 4 slang : a prison guard
▪ Tighten the screws. — see picture at carpentry; compare 1nail 1
b : a sexual partner
have a screw loose or have a loose screw
informal : to be crazy
▪ He acts like he has a screw loose. ▪ You've got to have a loose screw to think that's a good idea. = You've got to have a few loose screws to think that's a good idea.
▪ He acts like he has a screw loose. ▪ You've got to have a loose screw to think that's a good idea. = You've got to have a few loose screws to think that's a good idea.
put the screws on/to (someone or something)
informal : to use force or the threat of force to make (someone or something) do what you want
▪ The government is finally putting the screws to an industry that's been evading environmental laws for years.
▪ The government is finally putting the screws to an industry that's been evading environmental laws for years.
tighten the screws
informal : to put more pressure on someone or something to do something
▪ We need to tighten the screws on people who've been evading the tax.
▪ We need to tighten the screws on people who've been evading the tax.
