What does 'slip up' mean?

[Slippy]

English Language Tests, Intermediate level

ESL/EFL Test #655 "English Slang Idioms (397)", question 1

"You shouldn't've embarrassed her in front of her boss. Now she'll be waiting for you to slip ........., and if you do, she'll fire you. She's a very vengeful person," Chen said to Eric.

(a) down
(b) up
(c) short
(d) out

English Language Tests, Intermediate level

ESL/EFL Test #655 "English Slang Idioms (397)", answer 1

"You shouldn't've embarrassed her in front of her boss. Now she'll be waiting for you to slip up, and if you do, she'll fire you. She's a very vengeful person," Chen said to Eric.

Correct answer: (b) up

Your answer was: incorrect
"You shouldn't've embarrassed her in front of her boss. Now she'll be waiting for you to slip out, and if you do, she'll fire you. She's a very vengeful person," Chen said to Eric.
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the meaning of slip up =

[Alan]

Hi,

'Slip up' means make a small mistake.

Alan
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English as a Second Language
You can read my ESL story Present Simple