envelope

on the back of an envelope used in reference to calculations or plans of the most sketchy kind.

2013Daily Telegraph This two-boat, dual use idea has been dreamt up at the last minute on the back of an envelope, with no financial analysis.

push the envelope (or the edge of the envelope) approach or extend the limits of what is possible. informal

☞ This expression was originally aviation slang and related to graphs of aerodynamic performance on which the envelope is the boundary line representing an aircraft's capabilities.

2013New York Times Like so many [Robert] Stone characters, Brookman and Maud like to push the envelope; they enjoy the frisson of danger and are prone to equate heedlessness with freedom.

词组	envelope
释义	envelope on the back of an envelope used in reference to calculations or plans of the most sketchy kind. 2013Daily Telegraph This two-boat, dual use idea has been dreamt up at the last minute on the back of an envelope, with no financial analysis. push the envelope (or the edge of the envelope) approach or extend the limits of what is possible. informal ☞ This expression was originally aviation slang and related to graphs of aerodynamic performance on which the envelope is the boundary line representing an aircraft's capabilities. 2013New York Times Like so many [Robert] Stone characters, Brookman and Maud like to push the envelope; they enjoy the frisson of danger and are prone to equate heedlessness with freedom.
随便看	collect collect dust collect dust collect your wits collision colour colours column come come a cropper come again? come a gutser come a mucker come apart at the seams come apart at the seams come a purler come back (down) to earth (or bring someone back (down) to earth) come back to earth (or bring someone back (down) to earth) come clean come down in the world come down like a ton of bricks come down like a ton of bricks come down the pike come down to brass tacks come down to earth (or bring someone back (down) to earth)