na-adjective
Describes something that occurs at irregular intervals, stopping and starting repeatedly.
間欠的な雨が一日中降り続いた。
Intermittent rain continued all day.
この機械は間欠的に故障する。
This machine breaks down intermittently.
断続的 also means intermittent but often implies a more regular on-off pattern, while 間欠的 emphasizes irregular gaps.
Compound of 間欠 (intermittent) + 的 (-like, -ish). 間欠 is from 間 (interval) and 欠 (lack, gap).