Neat and trim.
A prim hedgerow.
To fix (the face or mouth) in a prim expression.
To make prim, as in dress or appearance.
To assume a prim expression.
Stiffly formal, precise, moral, etc.; proper; demure.
To assume a prim expression on (one's face or mouth)
The definition of prim is a proper, precise and formal person.
An example of prim is a traditional fifties housewife who does not wear casual clothes, and instead is always dressed as if she is ready to leave the house.
(dated) To dress or act smartly.
Origin of prim
Possibly from obsolete prim formal or demure person perhaps from Old French prin first, delicate prime