Definition of "gluten"

The radical or innate is daily supplied by nourishment, which some call cambium, and make those secondary humours of ros and gluten to maintain it […]

1624, Democritus Junior [pseudonym; Robert Burton], The Anatomy of Melancholy: […], 2nd edition, Oxford, Oxfordshire: Printed by John Lichfield and James Short, for Henry Cripps

[T]he Fly suspends it self very firmly and easily, without the access or need of any such Sponges fill'd with an imaginary gluten, as many have, for want of good Glasses, perhaps, or a troublesome and diligent examination, suppos'd.

1665, Robert Hooke, Micrographia, XXXVII

The tyrant machine is the female body, grinding and milling the pulp of matter, the gluten of human flesh.

1990, Camille Paglia, Sexual Personae

Chew on a small piece of dough, and it becomes more compact but persists as a gum-like, elastic mass, the residue that the Chinese named “the muscle of flour” and that we call gluten. It consists mainly of protein, and includes what may well be the largest protein molecules to be found in the natural world.

2004, Harold McGee, chapter 10, in On Food and Cooking: The Science and Lore of the Kitchen, Scribner

Unfortunately, wholemeal bread is, according to many experts, a tricky thing to get right, as the lower gluten content of the flour makes for dense results […]

2010 June 10, Felicity Cloake, Word of Mouth Blog, The Guardian

Despite constant rain that turned roads to gluten, the Yankees kept moving.

1988, James McPherson, Battle Cry of Freedom, Oxford, published 2004, page 669