Definition of "bah"

"To the doctor's? Bah!" said the sorceress, and spat upon the floor.

1886, Peter Christen Asbjørnsen, translated by H.L. Brækstad, Folk and Fairy Tales, page 301

Templeton looked over the assembled servants speculatively, then shrugged. "Bah!" he said. "They're of no use to me. Come, Andrew, a word with you upstairs."

1992, April Kihlstrom, Dangerous Masquerade

`There, cut his throat quick. Where is the saucer?' `The Goat! the Goat! the Goat! Give me the blood of my black goat! I must have it, don't you see I must have it? Oh! oh! oh! give me the blood of the goat.' At this moment a terrified bah! announced that the poor goat had been sacrificed, and the next minute a woman ran up with a saucer full of blood.

1886 October – 1887 January, H[enry] Rider Haggard, She: A History of Adventure, London: Longmans, Green, and Co., published 1887