Definition of turn up one's nose:
(v) :
(idiomatic, with "at") To regard with contempt or scorn; to treat with contempt or scorn; to ignore or disregard in a contemptuous or scornful way.
(v) :
(idiomatic, with "at") To refuse, especially with disgust, contempt or scorn; to refuse with apparent disregard about offending the offerer.
(v) :
To make the gesture of raising one's nose, as a sign of scorn, contempt or disgust.