1. fasten, tighten

make tight or tighter

Example Sentences:
'Tighten the wire'

• fasten

2. tighten

become tight or tighter

Example Sentences:
'The rope tightened'

3. constrain, stiffen, tighten, tighten up

restrict

Example Sentences:
'Tighten the rules'
'stiffen the regulations'

• constrain
• stiffen
• tighten up

4. reduce, tighten

narrow or limit

Example Sentences:
'reduce the influx of foreigners'

• reduce