conjunction
Casual spoken conjunction equivalent to それで. Used to connect clauses with a cause-and-effect or sequential relationship, often in informal conversation.
See also: それで
昨日は熱が出た。そいで、学校を休んだ。
I had a fever yesterday. And so I took the day off school.
道が混んでた。そいで、遅刻しちゃった。
The roads were crowded. So I ended up being late.