"Pfft, yeah right!"

Usage examples of pshaw.

To my surprise, however, Saxon pished and pshawed under his breath, until at last, unable to contain his impatience, he broke out in hot discontent.

Pshaw, my dear fellow, what do the public, the great unobservant public, who could hardly tell a weaver by his tooth or a compositor by his left thumb, care about the finer shades of analysis and deduction!