Chapter Longness to Loop of L by Webster's Dictionary (1913 Edition)

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.

Loop
(Loop) v. t. [imp. & p. p. Looped (l&oomacpt); p. pr. & vb. n. Looping.] To make a loop of or in; to fasten with a loop or loops; — often with up; as, to loop a string; to loop up a curtain.