jack (2) | jack shit
Meaning: nothing; very little
- Why don't you get out of the house and do something? You've been sittin' around doin' jack all day.
- Don't listen to John. He knows jack shit about how the economy works.
Variety: This slang is typically used in American English but may be used in other varieties of English too.
"That guy Kenny knows jack about playing poker." He knows