What does the "push the envelope" mean?

[Husni]

English Idioms and Expressions, Advanced Level

ESL/EFL Test #46 "Clothing Idioms (2)", question 6

However, when I asked him about his situation he told me not to worry because he has a card up his sleeve.

(a) he has a poker game tonight
(b) he has future gambling plans
(c) he has reserve plans that he stored and are available for future use

English Idioms and Expressions, Advanced Level

ESL/EFL Test #46 "Clothing Idioms (2)", answer 6

However, when I asked him about his situation he told me not to worry because he has reserve plans that he stored and are available for future use.

Correct answer: (c) he has reserve plans that he stored and are available for future use
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What does the ( push the envelope) mean?

Husni

[Linda]

To push the envelope means: To try and go/push beyond current limits/boundaries. It's an attempt to go past or to go further than accepted limits or boundaries."
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