Definition from Wiktionary, the free dictionary
Alternative forms 
Middle English flaunneol, from Anglo-Norman flanelle (cf. Jersiais flianné), diminutive of Old French flaine, floene 'coarse wool', from Gaulish vlanā ‘wool’ (cf. Welsh gwlân, Breton gloan). More at wool.
- Rhymes: -ænəl
- (uncountable) A soft cloth material woven from wool, possibly combined with cotton or synthetic fibers.
- With the weather turning colder, it was time to dig out our flannel sheets and nightclothes.
- 2012, Tom Lamont, How Mumford & Sons became the biggest band in the world (in The Daily Telegraph, 15 November 2012)
- 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.
- (New Zealand, UK) A washcloth.
- (slang) Soothing plausible untruth and half truth, claptrap - "Don't talk flannel" 
Derived terms 
soft cloth material
flannel (not comparable)
- made of flannel
made of flannel