W is for Weft (and warp) - noun. The threads that are passed over and under the warp threads to make cloth.
Of course, these things would have names. I actually learned these words from a recent program on television. Don't ask which program or channel. I wasn't paying that much attention. The weft (or woof) goes parallel to the loom (the thread on the shuttles) and the warp are the threads held by the loom.