The Oxford Thesaurus An A-Z Dictionary of Synonyms - tighten v.

1) Sometimes, tighten down or up. anchor, fasten, fix, tense, secure: Tighten those last two screws and you're finished. 2) make tighter or tenser or stronger, strengthen: He tightened his grip on my hand. 3) Sometimes, tighten up. make more rigorous or strict or stringent or severe or restrictive, close gaps in: We ought to tighten security at the warehouse. 4) Sometimes, tighten up. tauten, stiffen, tense, close: I felt the noose begin to tighten round my neck.