Complete fun or completely fun.

[david11]

1)The day was completely fun.

2)The day was complete fun.

I think the first one is correct and second one will be acceptable if a is added before complete.

[Tdol]

Neither works very well for me. I'd use something like great fun.

[david11]

Neither works very well for me. I'd use something like great fun.

Yours maybe appropriate but I just want to know the difference between those.

[emsr2d2]

There is no difference between the two you posted - they are both incorrect.

[david11]

There is no difference between the two you posted - they are both incorrect.

Really? I hear a lot people using it here.Could you please explain which part is incorrect?

[Tdol]

You will hear it used with both adjectives (tremendous fun) and adverbs (really fun). Do not use the indefinite article.

[JMurray]

1)The day was completely fun.
2)The day was complete fun.
I think the first one is correct and second one will be acceptable if a is added before complete.

Like Tdol, I don't find these to be very natural. However, it's possible that either might be heard in informal conversation, although I don't know which would be more likely.
The second one is definitely not improved by the addition of "a", to my mind it would become incorrect.

not a teacher