何とも言えない

indescribable

→ 何
phrase Rare #32,518
indescribable Also commonly means “hard to say” or “I can't put it into words,” depending on context. 何とも言えん is a more casual shortened form.
JA: この映画の結末は何とも言えない気持ちにさせる。
EN: The ending of this movie leaves me with an indescribable feeling.

何とも言えない

It's hard to say.

— ラスト、コーション (2007)

何とも言えない

I can't really say.

何とも言えない

I can't really say.

彼女はけっして美人ではないが何とも言えない愛敬がある

She’s by no means beautiful, but she has an indefinable charm.