~わずごろん

[katafei]

夕暮れ時、空もきれいで緑の芝が気持ちよく今日も一日歩いたので思わずごろん。

I came across this word of formation twice, today, but I have no idea what it means exactly and I can't find it in the dict...Is this a kind of colloquial expression?

[NileCat]

思わず (can't help but)
ごろん　(imitative word describing to lie down)

I can see a lovely cat が、ごろん としている in your picture on the right.

[furrykef]

思わず (can't help but)

Note that the literal meaning of this is "without thinking" (the -zu form of 思う). The idea here is probably that if you can't help but do something, you do it automatically, i.e., without thinking about it.

- Kef

[katafei]

Okay, thanks people!
勉強になりました。