bifold

English

A bifold door.

Etymology

From bi- +‎ -fold.

Adjective

bifold (not comparable)

1. Twofold, double.
2. Of two kinds.
   • c. 1602, William Shakespeare, “The Tragedie of Troylus and Cressida”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):
     , Act V, Scene II, page 77:

     O madneſſe of diſcourſe, / That cauſe ſets vp with and againſt it ſelfe, / By-fould authority : where reaſon can reuolte / Without perdition, and loſſe aſſume all reaſon, / Without reuolt.

Noun

bifold (plural bifolds)

1. (carpentry) A door, window, shutter, or divider consisting of two equal panels hinged together so that it opens by folding the panels against each other.
   • 1989, Karla J. Nielson, Window Treatments, →ISBN, page 21:

     Wood-finished insulative shutters set as bifolds at the window.

   • 2008, Bill Patten, My Three Fathers, →ISBN:

     The doors to the left were bifolds and opened into a long living room.

   • 2012, Andy Engel, Taunton's Carpentry Complete, →ISBN, page 218:

     Although bifolds are typically sold in kits where the doors are already hinged together, they're a little fussier than sliders or twins.

   • 2015, Ian Berwick, Why Otters Hold Hands When They Sleep, →ISBN:

     The wall facing the ocean was all glass and could be folded back in sections, bifolds, to almost completely have no wall at all, just a fulllength balcony and the ocean.

2. A sheet of paper or cardboard folded in half along a crease down the center.
   • 2006, Betty Buchanan, Amy Beach, The Canticle of the Sun, →ISBN, page 87:

     AFSl is made up of thirteen bifolds, or fifty-two pages (each unfolded folio measuring 13.5 x 21 inches), beginning with the title page and continuing for fifty-one numbered pages.

   • 2008, Sophie Brookover, Elizabeth Burns, Pop Goes the Library, →ISBN, page 94:

     Anonymous Public Library Director "[We use our] website, calendar of events, bifolds for teens and children, school visits (playing book bingo), PR in newspapers and on county cable channel.

   • 2014, International Monetary Fund. Fiscal Affairs Dept, Bolivia: Fiscal Transparency Assessment, →ISBN:

     Cards, bifolds and trifolds with information on public finances, debt, municipal finances, and other economic issues.

3. A wallet, billfold, or carrying case with a single fold, so that it opens like a book.
   • 1998 July, Robert Frick, “What Your Wallet Says About You”, in Kiplinger's Personal Finance, volume 52, number 7, page 97:

     A 1996 survey showed that men under age 20 buy three times as many trifolds as bifolds. So a trifold wallet becomes a habit, even after it has expanded to the size and shape of a jumbo bar of soap.

   • 2000, Edmund Hulton, Anomaly, →ISBN, page 44:

     Simultaneously, Simon and Pat pulled black leather covered identification bifolds from their breast pockets and let the back flap fall down.

   • 2007, George Feild, Deadly Agendas: An Alec Caldwell Novel, →ISBN:

     Alec and Rob handed her their leather bifolds containing their picture identification with their badges pinned inside.

4. A crease or turn that causes something to double back on itself.
   • 1898, George Manville Fenn, Jungle and Stream: Or, The Adventures of Two Boys in Siam, page 238:

     I want to learn how to play, and that's all puzzles and problems, and what do I care when I go to play a game about parallels and bifolds?

   • 1928, Supreme Court Papers on Appeal from Order:

     ...in porous beds, which are known as reservoir beds, which are usually sandstones or porous limestones, trapped there usually, not always, under bifolds in the rocks or arches in the rocks known as anteclines, and nearly all oil, not all oil, but nearly all oil wells are found where such reservoir beds are drilled into on the top of such anteclines.