The Collaborative International Dictionary
Envelope \En"vel*ope\ (?; 277), Envelop \En*vel"op\ (?; 277), n.
That which envelops, wraps up, encases, or surrounds; a wrapper; an inclosing cover; esp., the cover or wrapper of a document, as of a letter.
(Astron.) The nebulous covering of the head or nucleus of a comet; -- called also coma.
(Fort.) A work of earth, in the form of a single parapet or of a small rampart. It is sometimes raised in the ditch and sometimes beyond it.
--Wilhelm.-
(Geom.) A curve or surface which is tangent to each member of a system of curves or surfaces, the form and position of the members of the system being allowed to vary according to some continuous law. Thus, any curve is the envelope of its tangents.
4. A set of limits for the performance capabilities of some type of machine, originally used to refer to aircraft; -- it is often described graphically as a two-dimensional graph of a function showing the maximum of one performance variable as a function of another. Now it is also used metaphorically to refer to capabilities of any system in general, including human organizations, esp. in the phrase push the envelope. It is used to refer to the maximum performance available at the current state of the technology, and therefore refers to a class of machines in general, not a specific machine.
push the envelope to increase the capability of some type of machine or system; -- usually by technological development.
Wiktionary
vb. (context intransitive idiomatic English) to go beyond established limits; to pioneer.
Usage examples of "push the envelope".
An alliance of government and industry, unfettered by so-called ethicists and alleged Luddites, who want to push the envelope on all facets of creation.
Another letter's arrived but he hasn't had a chance to sort through the mail and you push the envelope deep into a pocket, listening but not listening to his travel chat.
I tried to push the envelope farther than anyone else, and instead I built a crystal-lattice trap that had been invented years before, in a country that was falling apart!
Part of the problem for us was that SCCA doesn't allow the sort of modifications we wanted, and the folks in SERRA wanted to push the envelope of sportscar racing a bit more, more `experimental' stuff.
God was gracious enough to push the envelope until change happened.
This will push the envelope of construction techniques for our early modern refrigeration researchers.