From time to time: Irregularly; now and then; occasionally; not predictably; sometimes, but not regularly or very often. If you do something from time to time, you do it occasionally but not regularly.
As in Her daughters visited him from time to time when he was ill.
中文释义：不时，偶尔，间或，有时。常用来表述某事发生的频率。在合同或法律文书里常翻译为“不时，不定期。”与之意思相近的词有：occasionally, sometimes, now and then, at times. 在用法上无异，ooccasionally强调的是偶然；sometimes的频度要低；At times更多是描述人或者情况,有的时候会有稍微负面的语气(并不是总是)。
例句：From time to time he fired questions at me.（他不时向我提出许多问题。）