noun

• (weaving) The horizontal threads that are interlaced through the warp in a woven fabric.
  "It is all the more remarkable therefore that in one respect — weft colours — some of the pirnless looms are more versatile than conventional machines. Figure 6 shows the colour mechanism of a conventional loom designed to weave six colours of weft (there is never any problem about colour patterning in the warp)."
• (weaving) The yarn used for the weft; the fill.
• (hairdressing) A hair extension that is glued directly to a person′s natural hair.
  "Teaching tools include mannequins, slip-ons, hair wefts, rectangles, and profiles."

noun

• (obsolete) Alternative spelling of waif.
  "The gentle Lady, loose at randon left, / The greene-wood long did walke, and wander wide / At wilde aduenture, like a forlorne weft,"

phrase

• (aviation) Acronym of wing(s), engine(s), fuselage(s), tail(s), a mnemonic for airplane identification, of most the most identifiable parts of the aeroplane, that can be used to distinguish one aircraft from another.