Definition of flannel
1 a
: a soft twilled wool or worsted fabric with a loose texture and a slightly napped surface
b
: a napped cotton fabric of soft yarns simulating the texture of wool flannel
c
: a stout cotton fabric usually napped on one side
2
flannels plural
a
: flannel underwear
b
: outer garments of flannel;
especially
: men's trousers
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