goof up vs. goof off

[Lost_Soul]

English Language Tests, Intermediate level

ESL/EFL Test #193 "Phrasal Verbs (G to H)", question 7

The students ......... when the teacher left the room.

(a) goofed up
(b) goofed off
(c) goofed on

English Language Tests, Intermediate level

ESL/EFL Test #193 "Phrasal Verbs (G to H)", answer 7

The students goofed off when the teacher left the room.

Correct answer: (b) goofed off

Your answer was: incorrect
The students goofed up when the teacher left the room.
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Hi, everybody !

Why not "goof up" ?
(I saw in a dictionary that a man can goof up which means that he takes some drugs. Is it true?)

thanks !

[Mister Micawber]

.
If it is, it is too slangy for me. 'Goof up' more usually means 'make a mistake', which does not apply here; nor do students do drugs when their teacher leaves the classroom-- they do them after school behind the Dempsey Dumpster.
.
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Native English teacher at Mister Micawber's

[Svitlana_Morokhovych]

What does "goof off" mean?

[Esl_Expert]

Hello Svetlana,

You can find the definition of "goof off" in most dictionaries under the word "goof":
http://dictionary.reference.com/search?q=goof&r=66
http://dictionary.cambridge.org/define.asp?key=33842&dict=CALD


The hyphenated form, "goof-off", is used as a noun:
http://www.merriam-webster.com/dictionary/goof-off
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"My definition of a redundancy is an air-bag in a politician's car." ~ Larry Hagman

[Einy]

These three are completely used as expressions.
Goofed up : made a mistake
Goofed off : Failed to act or behave seriously, joked around, wasted time
Goofed on : teased someone the action of others teasing a victim