随性用英语可以说是"casual"或者"offhand"。

"Casual"源自拉丁语的"casa"，意为住所或家，它的原意指的是住家的着装和态度。在现代，"casual"常常用来描述一种随意、不拘束的着装或者态度。

例句：

I'm just going to wear something casual to the party.

我去派对的时候就随便穿点儿东西。

He has a very casual attitude towards work.

他工作的态度非常随意。

"Offhand"则源自拉丁语的"ob"和"manus"，意为"前面"和"手"。在现代，"offhand"常常指一种态度或者说话方式，表示不做准备，随意而且自然。

例句：

He gave me an offhand answer when I asked him about his plans.

当我问他的计划时，他给我一个随意的答案。

She has an offhand manner that makes her very approachable.

她的态度随意，让人很容易接近。