push the envelope 

to push it to the limit. to see how far you can go with something without getting caught.

Whoa she pushes the envelope in her risque music videos.

push the envelope by Some random dude,somewhere out there in the lonly November 4, 2003

push the envelope 

"stretch the limits" - to go further (in any field) than anyone or any group has done before. perhaps doing something that wasn't previously thought possible.

dude, that quadruple-backflip double-twist one-handed going backwards while blindfolded and sucking a lolly (deep breath) surf manoeuvre was really pushing the envelope.

push the envelope by Smiff November 3, 2003

push the envelope 

To outdistance everyone else in an activity - set a new standard or precedent

push the envelope by Anonymous November 3, 2003