Loop, n. [Cf. Ir. & Gael. lub loop, noose, fold, thong, bend, lub to bend, incline.] 1. A fold or doubling of a thread, cord, rope, etc., through which another thread, cord, etc., can be passed, or which a hook can be hooked into; an eye, as of metal; a staple; a noose; a bight.
That the probation bear no hinge, nor loop
To hang a doubt on. Shak.
2. A small, narrow opening; a loophole.
And stop all sight-holes, every loop from whence
The eye of Reason may pry in upon us. Shak.
3. A curve of any kind in the form of a loop.
4. (Telegraphy) A wire forming part of a main circuit and returning to the point from which it starts.
5. (Acoustics) The portion of a vibrating string, air column, etc., between two nodes; — called also ventral segment.
Loop knot, a single knot tied in a doubled cord, etc. so as to leave a loop beyond the knot. See Illust. of Knot.