1(when not followed by 不) at all times; always
2(idiom) (when followed by 不) at no time; never (Note: 无时无刻不|无时无刻不 therefore means "at no time not ...", i.e. "at all times".)
Example
tāng汤mǔ姆hé和mǎ玛lì丽wú shí wú kè无时无刻bú zài不在biàn lùn辩论。
汤姆和玛丽无时无刻不在辩论。
Tom and Mary argue with each other all the time.