tight·en 
/ˈtaɪtn̩/ verb
tight·ens; tight·ened; tight·en·ing /ˈtaɪtn̩/ verb : to make (something) tight or tighter or to become tight or tighter [+ obj] ▪ I'll tighten the screw. ▪ She tightened her hold on the handle. [no obj] ▪ His jaw muscles tightened.
tighten the noose — see noose
tighten the screws — see 1screw
tighten up [phrasal verb]
tighten up or tighten (something) up or tighten up (something) : to become more strict or effective or to make (something) more strict or effective
▪ Security around the building has tightened up recently. ▪ They tightened up security around the building. ▪ We installed new machines to tighten up the assembly line.
▪ Security around the building has tightened up recently. ▪ They tightened up security around the building. ▪ We installed new machines to tighten up the assembly line.
tighten your belt — see 1belt
