Definition of "flannel"

First singer and guitarist Marcus Mumford, wearing a black suit, then bassist Ted Dwane, in leather bomber and T-shirt. Next bearded banjo player Winston Marshall, his blue flannel shirt hanging loose, and pianist Ben Lovett, wrapped in a woollen coat.

2012 November 15, Tom Lamont, “How Mumford & Sons became the biggest band in the world”, in The Daily Telegraph‎

"The Witch of Endor was a fool to her, sir: bless you, she would make no more of raising every gentleman in the Bible out of these here beastly tombs than I should of growing cress on an old flannel."

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

I got a little cross and asked him to stop flannelling and to tell me what was holding me back. Were my annual assessments below par? Was there something I had done – or not done?

2016, J. F. Langer, From the Spitfire Cockpit to the Cabinet Office