Dic: open the floodgates

• A decision against the cigarette companies could open the floodgates to many more lawsuits.
• If they win their case it could open the floodgates to others with similar compensation claims.
• The court's decision could open the floodgates for large numbers of other cases involving war crimes.
• Cf. It had opened the floodgates of her anxiety.

1. PHRASE : V inflects, usu PHR to/for n | If events open the floodgates to something, they make it possible for that thing to happen much more often or much more seriously than before.

2. If an action or a decision opens the floodgates, it allows something to happen a lot or allows many people to do something that was not previously allowed. (often + to )

3. to make it possible for something to happen.

• Usage notes: usually used to describe activities that had been difficult or illegal but which are now easier or allowed and expected to be done by many.
• Etymology: based on the literal meaning of open the floodgates (to allow water that had been held back to flow freely)

... Cobuild, Cambridge-Idioms, Cambridge-American Idioms,
http://idioms.thefreedictionary.com/floodgate

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floodgate: Noun.

1. a gate used to control the flow of water.
2. floodgates: controls against an outpouring of emotion.

.... Collins Essential