Previously
Before
noun
From before, just means previously or before now.
いぜん
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.
以前、パーティーで一どお会いしましたよね。
I met you once before at a party, right?
以前はよく船よいしていたんですが、今はさっぱりなくなりました。
I used to get seasick all the time, but not anymore.
私の親友は、以前は天文学者に知られていなかった惑星の出身です。
My best friend is from a planet that was previously unknown to astronomers.