off and on 偶尔；有时；断断续续地；不规则地；偶尔地；无依无靠的；间歇地；(航海)时而靠岸时而离岸地；断断续续

【例句】
You know, scientists have collected this kind of information off and on over the years, but a lot of it stays within the science community.
你知道，科学家们这些年断断续续地搜集了此类信息，但很多信息却保留在了科学圈内。

We lived together, off and on, for two years.
我们断断续续在一起生活了两年。