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1.
When a woman has a pair of shorts, trousers etc on that are so tight that the lips of her vagina are showing. The meaning is derived from being able to see some lips moving but not hearing a sound.
Dude, look - murmur pants alert
by vince-mcmahon March 13, 2010
 
2.
A reference to the tight leggings which reveal the lips of the vagina. Often worn in the high street. English Preston slang derived from murmur. 'I can see the lips moving but can't tell what the cunts saying'.
Check out the murmur pants on her.
by toeselecta July 26, 2011