Definition of "joist"

[…] a Family was infected there, in so terrible a Manner that every one of the House died; the last Person lay dead on the Floor, and as it is supposed, had laid her self all along to die just before the Fire; the Fire, it seems had fallen from its Place, being of Wood, and had taken hold of the Boards and the Joists they lay on, and burnt as far as just to the Body, but had not taken hold of the dead Body […]

1722, Daniel Defoe, A Journal of the Plague Year‎, London: E. Nutt et al., page 190

There are generally forty-two teeth in all; in old whales, much worn down, but undecayed; nor filled after our artificial fashion. The jaw is afterwards sawn into slabs, and piled away like joists for building houses.

1851 November 14, Herman Melville, chapter 74, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley

A formidable wooden beam, resting on four pillars, which appeared to have bent under the weight of the decrepit house, had been encrusted with as many coats of different paint as there are of rouge on an old duchess’s cheek. In the middle of this broad and fantastically carved joist there was an old painting representing a cat playing rackets.

1895, Honoré de Balzac, translated by Clara Bell, At the Sign of the Cat and Racket‎, London: J.M. Dent, published 1842, page 17

[…] even the carpenters who made her over for the service had not thought her worth the trouble, and had done their worst by her. The new partitions were hung to the joists by a few nails.

1923, Willa Cather, One of Ours‎, Book Four, Chapter 6

Once the floor joists were in position, the framing of the next storey could continue, with a bressummer laid along their ends.

1986, R. J. Brown, Timber-Framed Buildings of England, London: R. Hale, page 63

The floors are joisted with sapling tree trunks, and the flooring itself is made of bark, split and pounded flat into strips. No attempt is made either to fasten or join the strips of flooring.

2001, David Pickell, Between the Tides: A Fascinating Journey Among the Kamoro of New Guinea‎, revised edition, Hong Kong: Periplus, published 2002, Chapter Four, page 112