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1.
The silence that occurs after someone has said or done something that leaves everyone who bore witness to the event speechless.

The first cousin of awkward silence.

A pregnant pause often occurs when something that requires a sarcastic response happens, but no one quite knows what to day or do.
In the middle of a group of people having a conversation, Michael picks his nose and then eats it. All conversation ceases.

(pregnant pause)
by jcsavestheday August 22, 2008
 
2.
Delay in speech used to give one time to consider the consequences of a statement.
John took the microphone and asked Sarah to marry him. There was a pregnant pause while he, and the 3000-strong audience, waited for an answer.

or

Cars cause pollution that cause global warming..... (pregnant pause).... so when we need a pint of milk, maybe we should walk the 1/4 mile to the store instead of driving!
by MichelleM September 30, 2006
 
3.
1. Unexpected, annoying delay.
When reading and sending email across Wide Area Network, sometimes there is a pregnant pause, where the application stops your world waits for the hourglass...
by justin4fun April 14, 2006