The Month Before Last
Noun
せんせんげつ
先々月、キューバにりょこうにいきました。
I took a trip to Cuba the month before last.
先々月、シアトル市で大あめがふったせいで、市のめいぶつの玉ねぎばたけがぜんめつしてしまった。
Two months ago, due to the heavy rain in the city of Seattle, the city's famous onion field was entirely destroyed.
お母さんが先々月の携帯電話代を払ってくれた。
My mom paid my cellphone bill the month before last.
The previous previous month (remember that 々 just repeats the kanji before it) is the month before last.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.