She pursed her lips and took a prim sip of tea.
: Stiffly formal and respectable; feeling or showing disapproval of anything regarded as improper. com/en/definition/prim ) A sip can itself hardly literally be "prim", but of course we understand the word to refer to this lady's demeanour as she sipped.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
"prim" here has its ordinary meaning, such as you will find in a dictionary, e.g.:
Stiffly formal and respectable; feeling or showing disapproval of anything regarded as improper.
(https://www.lexico.com/en/definition/prim)
A sip can itself hardly literal