Vague
noun
Something with a vague nature is also quite vague.
ばくぜん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
漠然とした不安を感じながら、私は川の流れを見詰めていました。
While I was looking at the flow of the river I had a vague feeling of anxiety.