An onomatopoeic adverb indicating something happening slowly but steadily or spreading gradually (similar to じわりと).
コーヒーの湯気がじわっと顔に当たって心地よかった。
The steam from the coffee gently touched my face, which felt pleasant.
怪我は浅かったが、時間がたつとじわっと痛みが広がった。
The wound was shallow, but over time the pain slowly spread.
新商品の評判がSNSでじわっと広がっている。
Word about the new product is steadily spreading on social media.