/'taɪtn; `taɪtn/
v
1 [I, Ipr, Ip, Tn, Tn.pr, Tn.p] ~ (sth) (up)
(a) (cause sth to) become tight or tighter （使某物）变紧
*This screw needs tightening. 这螺钉需再拧紧些.
* tighten (up) the ropes 拉紧绳子
* He tightened his grip on her arm. 他紧抓住她的手臂.
(b) (cause sth to) become stricter （使某事）变得更严格
*Controls have gradually tightened. 控制逐渐加强.
* tighten up security 使安全措施更严密.
2 (idm 习语) loosen/tighten the purse-strings => purse. tighten one's `belt eat less food, spend less money, etc because there is littleavailable 勒紧腰带（省吃俭用）
*The management warnedof the need for further belt-tightening, ie economy. 资方提醒有必要进一步节约.
3 (phr v) tighten up (on sth) become more careful, vigilant or strict 变得更小心、警惕或严格
*The police are tightening up on drunken driving. 警方目前采取严厉手段对付醉酒驾车行为.

v alsotighten up
[T]
to close or fasten something firmly by turning it
≠ loosen
　Tighten the screws firmly.
　I'd put the new tyre on, but I hadn't tightened up the wheel.
[I and T]
if you tighten a rope, wire etc, or if it tightens, it is stretched or pulled so that it becomes tight
　When you tighten guitar strings, the note gets higher.
　The rope tightened around his body.
[I and T]
to become stiff or make a part of your body become stiff
≠ relax
　His mouth tightened into a thin, angry line.
　Tighten up the muscles of both arms.
tighten your grip/hold on sth
a) to control a place or situation more strictly
　Rebel forces have tightened their hold on the capital.
b) to hold someone or something more firmly
　Sarah tightened her grip on my arm.
[T]
to make a rule, law, or system more strict
≠ relax
　Efforts to tighten the rules have failed.
tighten up on sth
　a range of measures to tighten up on illegal share dealing
tighten your beltinformal
to try to spend less money than you used to
　Businesses were tightening their belts and cutting jobs.
tighten the screws (on sb)informal to try to force someone to do something, by threatening them or making things difficult for them - used in news reports
　Closing the border would tighten the screws on the terrorists.
[I]American English if a race or competition tightens, the distance between the competitors becomes smaller
　He expects the presidential race to tighten.
tighten upphr v
if a team or group tightens up, they start working together more effectively
tighten sth⇔up
　We have tightened up the defence and are winning matches as a result.