To be able to express something in words; the potential form meaning that something can be put into words.
彼は自分の気持ちを正確に言い表せる人だ。
He is someone who can express his feelings precisely in words.
この喜びは言い表せるほど大きくはない。
This joy is too great to be fully put into words.
複雑な感情は、必ずしも他人に言い表せるものではない。
Complex emotions are not necessarily something you can express to others in words.