Definition of "pfui"

'Pfui!' The captain spat. 'I've never met such a dumb sailor as you. So where do you think the old moon goes?'

1981, Charles H. Kahn, The Art and Thought of Heraclitus

She liked Arschlochweh and adored Improvisation; but the Anatomiestunde and the bending and stretching she did not like. "Pfui!" she was disgusted, lifting her shoulders and spreading her hands like the Mandarin, "pfui! the old body!'

1993, Samuel Beckett, Eoin O'Brien, Edith Fournier, Dream of Fair to Middling Women, page 14

He comes barging in here as if the place belonged to him. And intoxicated . . pfui! . . the disgusting pig!

2008, Christopher Isherwood, The Berlin Stories, page 175