GR translation: but def, after weeks of his snide comments?

[Mike Jing]

"but really", now I understand.  Thanks, János.

On Tue, May 8, 2012 at 2:08 AM, János Széky <miksaapja at gmail.com> wrote:
> Abbreviation of "but definitely", that's "but really", as in the
> Shirley Temple song, a kind of Americanized British wartime middle
> class female slang.
>
> The question mark refers to the contrast between Roger's (probably)
> agnostic and anti-Christmas bickering and the sudden impulse to enter
> the chapel on Christmas eve. "How come?"
>
>
> János
>
>
> 2012/5/8 Mike Jing <gravitys.rainbow.cn at gmail.com>:
>> P130.15-22   Roger pulled over, and they watched the scuffed and dun
>> military going in to evensong. The wind smelled of fresh snow.
>>            “We ought to be home,” she said, after a bit, “it’s late.”
>>            “We could just pop in here for a moment.”
>>            Well, that surprised her, but def, after weeks of his
>> snide comments? His unbeliever’s annoyance with the others in Psi
>> Section he thought were out to drive him dotty as they were, and his
>> Scroogery growing as shopping days till Xmas dwindled—
>>
>> What exactly does "but def" mean here?  Why is there a question mark
>> at the end of the sentence?