FAQs About the word once in a blue moon

罕见

very rarely

不经常,少,偶尔,很少,有时,绝不,永远不,时不时地,很少,零星地

总是,永远,频繁地,一般,经常,通常,例行地,通常,始终,不断地

on-and-off => 时有时无, on top of => 在…之上, on tiptoe => on tiptoe, on the warpath => 处于战备状态, on the surface => 表面上,