v. 25B6; verb
I tightened up the screws : MAKE TIGHTER, make fast, screw up.
he tightened his grip : STRENGTHEN, make stronger, harden.
she tightened the rope : TAUTEN, make/draw taut, make/draw tight, stretch, strain, stiffen, tense.
he tightened his lips : NARROW, constrict, contract, compress, screw up, pucker, purse; N. Amer. squinch.
security in the area has been tightened up : INCREASE, make stricter, toughen up, heighten, scale up.
loosen, slacken, relax.