To be gullible, na?ve, or unsophisticated. The subject is often a person from a rural or rustic background. Mary has no idea about how to act in polite society, always behaving as if she just fell off the turnip truck.
Rur. ignorant; unsophisticated. He stood there gawking at the buildings in town like he just fell off the turnip truck.My cousin acts like she just fell off the turnip truck.
Prov. You cannot get help from an uncharitable person or money from someone who has none. Jerry and James spent two hours trying to convince the old miser to contribute to the children's hospital; finally, James turned to Jerry and said in disgust, "This is hopeless. We can't get blood from a stone." The government can't increase taxes any further—nobody has the money! You can't get blood from a turnip.