not know jack
The phrase "not know jack" is an idiom meaning to have little or no knowledge or understanding about a particular topic or situation. It suggests a lack of familiarity or ignorance about something.
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You will never be “out of your element” thanks to multiple difficulty levels and phrase libraries provide idiom puzzles for all levels from students to English learners to fluent adult English speakers.
Just Saying is “the real McCoy” of phrase games!