Pshaw

Part of speech: verb (v.)

To express disgust or contemptuous disapprobation, as by the exclamation " Pshaw!" The goodman used regularly to frown and pshaw wherever this topic was touched upon. Sir W. Scott.

Part of speech: interjection (interj.)

Pish! pooch! -- an exclamation used as an expression of contempt, disdain, dislike, etc. [Written also psha.]