also: さきおとつい · さきおととい
two days before yesterday; three days ago
Refers to the day three days before today. The reading いっさくさくじつ is the most standard; さきおとつい and さきおととい are colloquial or dialectal variants. Used both as a noun and adverbially.
一昨昨日は大雨だった。
Three days ago, there was heavy rain.
I still have the newspaper from three days ago.
I've had a headache since three days ago.
There was heavy rain on the night of three days ago.
Colloquial or dialectal kana form for the reading さきおとつい; not standard in writing.